test: Add delay to upcoming mtg filter tests

[jennifer-richards]

Hopefully this will fix the transient failures around the do_upcoming_view_filter_test helper

This is the quick-and-dirty approach - could be smarter and use a WebDriverWait if something unexpected is encountered, but that will require some care so let's see if this works first. Probably adds ~5 seconds to the testing time because there are 22 tests using the helper.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (d1909fd) 88.82% compared to head (06b0630) 88.83%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6707   +/-   ##
=======================================
  Coverage   88.82%   88.83%           
=======================================
  Files         285      285           
  Lines       40224    40224           
=======================================
+ Hits        35730    35731    +1     
+ Misses       4494     4493    -1     

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