fix: Remove custom Accept headers from search endpoints

[alexandear]

The PR removes deprecated preview "Accept" headers from all search endpoints.

The REST API for search was fully launched a long time ago https://docs.github.com/en/rest/search/search

[alexandear]

We can't remove preview constants yet:

$ grep -r --include='*.go' --exclude='*_test.go''mediaTypeTopicsPreview'../github/repos_forks.go: req.Header.Set("Accept", mediaTypeTopicsPreview)./github/teams.go: req.Header.Set("Accept", mediaTypeTopicsPreview)./github/teams.go: req.Header.Set("Accept", mediaTypeTopicsPreview)./github/activity_star.go: acceptHeaders := []string{mediaTypeStarring, mediaTypeTopicsPreview}./github/repos.go: acceptHeaders := []string{mediaTypeTopicsPreview, mediaTypeRepositoryVisibilityPreview}./github/repos.go: mediaTypeTopicsPreview,./github/repos.go: req.Header.Set("Accept", mediaTypeTopicsPreview)./github/repos.go: req.Header.Set("Accept", mediaTypeTopicsPreview)./github/github.go: mediaTypeTopicsPreview = "application/vnd.github.mercy-preview+json"
$ grep -r --include='*.go' --exclude='*_test.go''mediaTypeReactionsPreview'../github/issues.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/issues.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/issues.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/issues_comments.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/issues_comments.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/reactions.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/reactions.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/reactions.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/reactions.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/reactions.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/reactions.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/reactions.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/reactions.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/reactions.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/reactions.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/reactions.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/reactions.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/reactions.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/reactions.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/reactions.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/repos_comments.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/repos_comments.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/repos_comments.go: req.Header.Set("Accept", mediaTypeReactionsPreview)./github/pulls_comments.go: acceptHeaders := []string{mediaTypeReactionsPreview, mediaTypeMultiLineCommentsPreview}./github/pulls_comments.go: acceptHeaders := []string{mediaTypeReactionsPreview, mediaTypeMultiLineCommentsPreview}./github/pulls_comments.go: acceptHeaders := []string{mediaTypeReactionsPreview, mediaTypeMultiLineCommentsPreview}./github/github.go: mediaTypeReactionsPreview = "application/vnd.github.squirrel-girl-preview"

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.32%. Comparing base (9c16433) to head (a068ebe).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@ Coverage Diff @@## master #3820 +/- ##
==========================================
- Coverage 92.32% 92.32% -0.01% 
==========================================
Files 194 194 Lines 13984 13973 -11 ==========================================
- Hits 12911 12900 -11 
Misses 884 884 Partials 189 189 

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[gmlewis]

Thank you, @alexandear!
LGTM.
Awaiting second LGTM+Approval from any other contributor to this repo before merging.

cc: @stevehipwell - @zyfy29

[stevehipwell]

LGTM

[gmlewis]

Thank you, @stevehipwell!
Merging.