chore: udpate functional test version to 4.26 (#142)

Author: austinletson

.github/workflows/functional_tests.yml

@@ -13,12 +13,12 @@ on:
       toolchain:
         description: "The Lean toolchain to use when running the tests."
         required: false
-        default: "leanprover/lean4:v4.21.0"
+        default: "leanprover/lean4:v4.26.0"
 
 # This environment variable is necessary in addition to the workflow_dispatch input
 # because the workflow_dispatch input is not available when the workflow is triggered by a pull request
 env:
-  toolchain: ${{ github.event.inputs.toolchain || 'leanprover/lean4:v4.21.0' }}
+  toolchain: ${{ github.event.inputs.toolchain || 'leanprover/lean4:v4.26.0' }}
 
 jobs:
   lake-init-success: