remove obsolete comment in AtEOXact_Inval

Hi, Hackers,

When I read the code, I noticed there is one line of comment in function AtEOXact_Inval() which is obviously obsolete.

    "This should be called as the last step in processing a transaction"  

AtEOXact_Inval() is called in CommitTransaction() and AbortTransaction() and there are many other steps after function AtEOXact_Inval() is called.

Such as:

      AtCommit_Notify();

      AtEOXact_GUC(true, 1);

      AtEOXact_SPI(true);

      AtEOXact_Enum();

      AtEOXact_on_commit_actions(true);

      AtEOXact_Namespace(true, is_parallel_worker);

      AtEOXact_SMgr();

      AtEOXact_Files(true);

      AtEOXact_ComboCid();

      AtEOXact_HashTables(true);

      AtEOXact_PgStat(true, is_parallel_worker);

      AtEOXact_Snapshot(true, false);

      AtEOXact_ApplyLauncher(true);

      AtEOXact_LogicalRepWorkers(true);

So that comment is no longer true. I made a patch to remove it as attached.

Best Regards,

Steven