remove linux & mac from CI

Author: Npella

.github/workflows/Pharo11CI.yml

@@ -14,7 +14,7 @@ jobs:
   build:
     strategy:
       matrix:
-        os: [ ubuntu-latest, macos-latest, windows-latest ]
+        os: [ windows-latest ]
         smalltalk: [ Pharo64-11 ]
     runs-on: ${{ matrix.os }}
     name: ${{ matrix.smalltalk }} on ${{ matrix.os }}