test(ci): only install headless shell chromium for playwright

[max-nextcloud]

Speeds up the installation of the browsers drastically:

scenario	1st run	2nd run	3rd run	avg
all browsers	53 sec	74 sec	59 sec	~ 62 sec
only chromium --with-deps	42 sec	29 sec	31 sec	~ 34 sec
chromium --with-deps --only-shell	22 sec	18 sec		~ 20 sec
chromium --only-shell	4 sec	5 sec		~ 4.5 sec

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 43.40%. Comparing base (929a649) to head (b9d7c35).
Report is 13 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #2544   +/-   ##
=========================================
  Coverage     43.40%   43.40%           
  Complexity      882      882           
=========================================
  Files            77       77           
  Lines          3359     3359           
=========================================
  Hits           1458     1458           
  Misses         1901     1901