ci: Fix check-changes job skipping over YAML changes. (#8377)

This commit fixes a copy/paste error from #8356 that resulted
in the YAML detection logic of the `check-changes` job setting
the wrong result for the job step's yaml changes output.

This bug caused downstream jobs to not see that YAML files were
altered at all in a PR, and YAML-specific jobs like the linter
and zizmor passes would not be run.

Signed-off-by: Philip Conrad <philip@chariot-chaser.net>

Author: philipaconrad

.github/workflows/pull-request.yaml

@@ -71,7 +71,7 @@ jobs:
         wasm_result=$(jq -r '.changes.wasm // false' opa_result.json)
         docs_result=$(jq -r '.changes.docs // false' opa_result.json)
         rego_result=$(jq -r '.changes.rego // false' opa_result.json)
-        yaml_result=$(jq -r '.changes.rego // false' opa_result.json)
+        yaml_result=$(jq -r '.changes.yaml // false' opa_result.json)
 
         echo "go=${go_result}" >> $GITHUB_OUTPUT
         echo "wasm=${wasm_result}" >> $GITHUB_OUTPUT