chore: Revert agenda editor font change (#6538)

* Revert "fix: Change some colors to make agenda tool work in dark mode (#6428)"

This reverts commit 699a8e2.

* Revert "Revert "fix: Change some colors to make agenda tool work in dark mode (#6428)""

This reverts commit 5adafac.

* chore: Revert only font-family change

* chore: Add comment to ietf.scss

ietf/static/css/ietf.scss

@@ -744,7 +744,8 @@ td.position-empty {
 
 .edit-meeting-schedule .edit-grid,
 .edit-meeting-schedule .session {
-    // font-family: arial, helvetica, sans-serif;
+    // Removing this font-family style causes selenium tests to fail :-(
+    font-family: arial, helvetica, sans-serif;
     font-size: 11px;
 }