ci: fix 'TYPE' variable usage

I *think* this way should have worked, but it doesn't [1].

So let's use an actual variable instead of interpolation, which *should*
work.

[1]: https://github.com/woodpecker-ci/woodpecker/issues/2068

.woodpecker/deploy.yml

@@ -17,7 +17,7 @@ matrix:
 when:
   evaluate: |
     CI_PIPELINE_EVENT in ["push", "cron", "deployment", "manual"]
-    and ((CI_COMMIT_BRANCH == CI_REPO_DEFAULT_BRANCH) == ("${TYPE}" == "prod"))
+    and ((CI_COMMIT_BRANCH == CI_REPO_DEFAULT_BRANCH) == (TYPE == "prod"))
 
 pipeline:
 - name: check