Pull ircservserv from GitLab, don't pin commit

The pinning of the commit was only needed to bypass blubber's
caching, which shouldn't be needed here.

.gitlab-ci.yml

@@ -3,8 +3,7 @@ stages:
 
 variables:
   CARGO_BUILD_JOBS: "1"
-  IRCSERVSERV_REPO: "https://gerrit.wikimedia.org/r/wikimedia/irc/ircservserv"
-  IRCSERVSERV_REV: "f5f4d95"
+  IRCSERVSERV_REPO: "https://gitlab.wikimedia.org/toolforge-repos/ircservserv"
 
 test-validate:
   stage: test
@@ -15,5 +14,5 @@ test-validate:
     - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
   image: rust:latest
   script:
-    - cargo install --locked --git $IRCSERVSERV_REPO --rev $IRCSERVSERV_REV
+    - cargo install --locked --git $IRCSERVSERV_REPO
     - /usr/local/cargo/bin/validate-config channels