Unfork fmt/core.h

[marlenecota]

Summary

We forked fmt to fix a CodeQL error: #13281
The fix is merged upstream, but we're waiting on a new release: fmtlib/fmt#3945

Motivation

#12702

[jonthysell]

It looks like the fix got released in fmt 11.0 - @chiaramooney can you see about bumping our fmt version (to at least 11.0) so we can close this? Should be a straight forward PR to unfork the files, and bump the fmt version/commit hash and verify it all builds.