Code Modernization: Remove obsolete comments about older PHP versions.
This commit:
- Removes various comments referencing PHP versions which are no longer supported.
- Removes various comments containing “hints” of things to do after a particular PHP version drop. These hints are incorrect/not actionable for various reasons, so have no value:
- Even though a function could be turned into a closure, removing the function would be a backward compatibility break which is not acceptable, so this suggestion is not actionable.
- Short ternaries are forbidden by the coding standard exactly to prevent the faulty code suggested in the comment from getting into the codebase.
Follow-up to [1243/tests], [6543], [11816], [29861], [29864], [34928], [35369], [36698], [38694], [50786], [58678].
Props jrf, ayeshrajans.
See #61574.