fix: invert addTimeStamp config logic

[oojacoboo]

Summary

• The generator.objectModel.addTimeStamp config option had inverted logic: setting it to true suppressed timestamps, while false (the default) included them.
• This flips the condition in generateTimestampBlock() so the config behaves as its name suggests — true adds timestamps, false omits them.

Note: the baseQueryClassHeader.php template already had the correct logic (if ($addTimestamp) → show timestamp). This fix brings AbstractOMBuilder in line with the template.

Impact

Projects using the default addTimeStamp: false will no longer get timestamps in generated class headers, eliminating unnecessary noise in version control diffs.

[mringler]

I am confused.

This was already fixed in c08d88f (reference files don't work when timestamps are generated).
And indeed it seems to be the same as the current state in main: https://github.com/perplorm/perpl/blob/main/src/Propel/Generator/Builder/Om/AbstractOMBuilder.php#L618

Why is this showing up as changing something? Am I stupid this morning or what?

[oojacoboo]

Oh, 2 days ago - wow okay. I think the issue is that my fork wasn't synced for the main branch maybe. Not really sure b/c I know I synced it before starting on the other PR. But maybe this fix came after. Closing as already fixed.