fix(gitpod): correct command name (#13976)

`leanpkg config` doesn't exist, it's `leanpkg configure`.

@b-mehta tricked me in #13949 (comment)

.gitpod.yml

@@ -6,5 +6,5 @@ vscode:
     - jroesch.lean
 
 tasks:
-  - init: leanpkg config && leanproject get-cache --fallback=download-all
+  - init: leanpkg configure && leanproject get-cache --fallback=download-all
     command: . /home/gitpod/.profile