Fix browser deprecations in Pharo 11

[marschall]

This should help with all the deprecation warnings on Pharo 12 in logs.

[codecov]

Codecov Report

Attention: Patch coverage is 54.28571% with 16 lines in your changes missing coverage. Please review.

Project coverage is 48.27%. Comparing base (3074c69) to head (1cd0101).

Files	Patch %	Lines
...RPackageBasedBrowser.class/instance/messageList.st	0.00%	12 Missing ⚠️
.../WARPackageBasedBrowser.class/instance/contents.st	0.00%	3 Missing ⚠️
...dBrowser.class/instance/systemCategoryListIndex.st	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1421   +/-   ##
=======================================
  Coverage   48.27%   48.27%           
=======================================
  Files        9116     9117    +1     
  Lines       81731    81748   +17     
=======================================
+ Hits        39452    39464   +12     
- Misses      42279    42284    +5     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[jbrichau]

thanks!