.github/workflows: fix wiki.yml

tools/docs2wiki is moved to ./extension directory.

For #3122

Change-Id: I6cc21764b707b0577765aef1c06718fdd494f460
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/556857
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
Reviewed-by: Suzy Mueller <suzmue@golang.org>
Auto-Submit: Hyang-Ah Hana Kim <hyangah@gmail.com>
Commit-Queue: Hyang-Ah Hana Kim <hyangah@gmail.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>

Author: hyangah

.github/workflows/wiki.yml

@@ -43,7 +43,7 @@ jobs:
       - name: Push to wiki
         run: |
           cd vscode-go
-          go run ./tools/docs2wiki -w ./docs
+          go run -C extension ./tools/docs2wiki -w ../docs
           cd ..
           cd wiki
           rm -r ./* && cp -r ../vscode-go/docs/* .