Update fix_doctests.yml

Fix julia-version argument.

Author: andreasnoack

.github/workflows/fix_doctests.yml

@@ -7,7 +7,8 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        julia-version: '1.10'
+        julia-version:
+          - '1.10'
     steps:
       - uses: actions/checkout@v4
       - uses: julia-actions/setup-julia@latest