[LINTER] Fix the doxygen linter when inline comments are multilined

Summary:
Fix the false positive case found in
https://reviews.bitcoinabc.org/D5239?id=16218#inline-32123.

Test Plan:
Edit a source file to create a situation similar to
https://reviews.bitcoinabc.org/D5239?id=16218#inline-32123 and run:

arc lint -- <your_file>

Check the linter don't report any autofix.

Edit again to add a new line like:

//!< This should not occur

Check the linter autofixes this comment.

arc lint --everything

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D5240