fix: issue with `_save_screenshot()`

[jrycw]

It seems that we need to use f.read() to avoid the TypeError: a bytes-like object is required, not '_io.BufferedReader'.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 85.90%. Comparing base (6b2624b) to head (c0ea247).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #352      +/-   ##
==========================================
+ Coverage   85.74%   85.90%   +0.16%     
==========================================
  Files          41       41              
  Lines        4328     4328              
==========================================
+ Hits         3711     3718       +7     
+ Misses        617      610       -7     

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[machow]

Merged in main so we could re-run tests