Update branch.yaml

Remove Python 3.12 from build workflow.

Author: josteinl

.github/workflows/branch.yaml

@@ -6,7 +6,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ['3.9', '3.10', '3.11', '3.12']
+        python-version: ['3.9', '3.10', '3.11']
         poetry-version: ['1.6.1']
         os: [ubuntu-latest]
     runs-on: ${{ matrix.os }}
@@ -29,7 +29,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ['3.9', '3.10', '3.11', '3.12']
+        python-version: ['3.9', '3.10', '3.11']
         poetry-version: ['1.6.1']
         os: [ubuntu-latest]
     runs-on: ${{ matrix.os }}