Indenting of test .cc file

[spco]

When calling ./doc/indent from the main directory, this picks up the file tests/resume_free_surface.cc and indents that. This is a bit annoying as this gets picked up as a tracked file and a call to git add -u, my usual, stages this change. I'm bound to unintentionally add this to a commit at some point.

Could we tweak the .cc file to have the correct indentation, or is there a better fix/should I use a different workflow?

[bangerth]

#628 introduced this, I think.

[bangerth]

Actually, it was #1110.