ci: update used terraform version to 1.13 (#744)

Signed-off-by: Nathanael Liechti <[email protected]>

Author: the-technat

.github/workflows/tests.yml

@@ -68,7 +68,7 @@ jobs:
       fail-fast: false
       matrix:
         argocd_version: ['v2.14.5', 'v3.0.0', 'v3.1.0']
-        terraform_version: ['1.4.*']
+        terraform_version: ['1.13.*']
     steps:
       - name: Check out code
         uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955 # v4.3.0