chore: Revert agenda editor font change

[jennifer-richards]

Using the default fonts apparently moves components around enough that selenium tests fail. Until we remove / debug those, go back to the non-standard fonts on the agenda editor "session" elements.

The failing test was EditMeetingScheduleTests.test_edit_meeting_schedule

[codecov]

Codecov Report

Merging #6538 (4b794a5) into main (f6a2d8c) will increase coverage by 0.13%.
Report is 38 commits behind head on main.
The diff coverage is 95.94%.

❗ Current head 4b794a5 differs from pull request most recent head 792365d. Consider uploading reports for the commit 792365d to get more accurate results

@@            Coverage Diff             @@
##             main    #6538      +/-   ##
==========================================
+ Coverage   88.70%   88.84%   +0.13%     
==========================================
  Files         290      284       -6     
  Lines       40440    40243     -197     
==========================================
- Hits        35874    35755     -119     
+ Misses       4566     4488      -78     

Files	Coverage Δ
ietf/doc/views_conflict_review.py	97.05% <100.00%> (-0.07%)	⬇️
ietf/secr/meetings/forms.py	89.33% <ø> (+0.16%)	⬆️
ietf/secr/meetings/urls.py	100.00% <ø> (ø)
ietf/secr/meetings/views.py	83.57% <100.00%> (+0.05%)	⬆️
ietf/secr/urls.py	100.00% <ø> (ø)
ietf/submit/parsers/base.py	96.72% <100.00%> (+1.56%)	⬆️
ietf/submit/parsers/xml_parser.py	100.00% <ø> (ø)
ietf/utils/xmldraft.py	93.18% <100.00%> (+0.26%)	⬆️
ietf/submit/forms.py	79.10% <80.00%> (+0.07%)	⬆️
ietf/submit/parsers/plain_parser.py	92.85% <91.66%> (+0.70%)	⬆️

... and 2 files with indirect coverage changes