docs: Replace JIRA with GitHub Issues

[Fokko]

And some general cleanup.

Rationale for this change

What changes are included in this PR?

Are these changes tested?

Are there any user-facing changes?

[ArnavBalyan]

LGTM! It seems there are some JIRA references in code https://github.com/apache/parquet-java/blob/master/parquet-column/src/main/java/org/apache/parquet/filter2/predicate/SchemaCompatibilityValidator.java#L57. Should they also point to Github now?

[ArnavBalyan]

LGTM! It seems there are some JIRA references in code https://github.com/apache/parquet-java/blob/master/parquet-column/src/main/java/org/apache/parquet/filter2/predicate/SchemaCompatibilityValidator.java#L57. Should they also point to Github now?

Maybe should be okay as JIRA has the corresponding GH link in the comment

[wgtmac]

@ArnavBalyan Yes, I think linking to old JIRA issues is fine. They are the history. New issues should go with Github issue but not JIRA.