Fix ordering of IncludeCategories in clang-format

[ncorsobh]

Proposed changes

A previous PR (#5690) had removed the duplicate entry of IncludeCategories in clang-format, assuming that the first one was being read. That assumption was incorrect, and the current version of IncludeCategories causes a conflict with the formatting options in clang-tidy. Although this version was added more recently to the file, it was decided that the other one was more preferable anyway, so this update switches the two. This removes the preference that pushes includes ending in .h to the beginning of the list.

Upgrade instructions

Code review checklist

• The code is documented and the documentation renders correctly. Run
  make doc to generate the documentation locally into BUILD_DIR/docs/html.
  Then open index.html.
• The code follows the stylistic and code quality guidelines listed in the
  code review guide.
• The PR lists upgrade instructions and is labeled bugfix or
  new feature if appropriate.

Further comments

[knelli2]

Merging quickly so people can rebase and have clang-format work properly