ENH: Add comments to MR template

Summary

Comment out sections of the merge request template that are sometimes not necessary. For example in the case of this MR.

Rationale

Clearer MR descriptions for small patches.

Implementation Details

Classes and files

Applications

Tests

Documentation

Additional notes

Copyright

The copyright owner is CNES and has signed the ORFEO ToolBox Contributor License Agreement

merged

mentioned in commit 8338764f

added documentation label

changed milestone to %7.0.0