Update PTtools version

Author: AgenttiX

.github/workflows/main.yml

@@ -41,10 +41,12 @@ jobs:
         uses: actions/checkout@v4
         with:
           repository: CFT-HY/pttools
-          # A specific commit is used instead of the 0.9.0 release,
-          # as the release is missing some __init__.py files in the example folders,
-          # which prevents the example scripts from being imported.
-          ref: da50329beba788803ba6bee2b497a89a98bea53d
+          # The 0.9.0 release was missing some __init__.py files in the example folders,
+          # which prevented the example scripts from being imported.
+          # In addition to this, the Giese et al. bubble solver has since been included in PTtools
+          # and removed from this repository.
+          # Both of these changes necessitate the use of a newer PTtools version than 0.9.0.
+          ref: a2941306f0168debe543595a02919957bb52add0
           path: pttools
       - name: Load pip cache
         uses: actions/cache@v4