Auto merge of #134199 - RalfJung:gitmerge, r=oli-obk

Revert "Stop git from merging generated files"
This reverts #133851. "-merge" makes git not even do merges if they are entirely conflict-free, which is not the behavior we want. We sometimes have conflict-free merges in generated files and it's much better if git can handle them automatically.
r? `@oli-obk`
Cc `@jieyouxu` `@Urgau`

Author: bors

.gitattributes

@@ -4,10 +4,8 @@
 *.cpprust
 *.hrust
 *.rsrustdiff=rust
-*.fixedlinguist-language=Rust-merge
-*.mirlinguist-language=Rust-merge
-*.stderr-merge
-*.stdout-merge
+*.fixedlinguist-language=Rust
+*.mirlinguist-language=Rust
 src/etc/installer/gfx/*binary
 src/vendor/**-text
 Cargo.locklinguist-generated=false