Update CI for Pharo 11 and 12

Author: guillep

.github/workflows/main.yml

@@ -20,10 +20,8 @@ jobs:
     strategy:
       matrix:
         smalltalk:
-          - Pharo64-10
-          - Pharo64-9.0
-          # Waiting a 32-bit version of Pharo 90 before re-enabling this version
-          #  - Pharo32-9.0
+          - Pharo64-12
+          - Pharo64-11
         smalltalk_config: [ .smalltalk.ston, .stress.smalltalk.ston ]
         os: [ ubuntu-latest, macos-latest ]
     runs-on: ${{ matrix.os }}