Add deps-docs command to makefile (#23686)

Refactored `deps-docs` out of `docs` because #23629 broke Gitpod's docs
setup (which grepped to get the hugo install command).

Now `make deps` really installs everything to develop (includes `docs`).

.gitpod.yml

@@ -24,8 +24,11 @@ tasks:
       make watch-frontend
     openMode: split-right
   - name: Run docs
-    before: sudo bash -c "$(grep 'https://github.com/gohugoio/hugo/releases/download' Makefile | tr -d '\')" # install hugo
-    command: cd docs && make clean update && hugo server -D -F --baseUrl $(gp url 1313) --liveReloadPort=443 --appendPort=false --bind=0.0.0.0
+    command: |
+      gp sync-await setup
+      cd docs
+      make clean update
+      hugo server -D -F --baseUrl $(gp url 1313) --liveReloadPort=443 --appendPort=false --bind=0.0.0.0
     openMode: split-right
 
 vscode: