.github/workflows: partially revert go.dev/cl/380175

Splitting into build + release jobs doesn't work as I thought.
Cloned repository state isn't shared between jobs obviously.
We should've built the artifact (.vsix) from the build stage,
pass the artifact location to the publish stage. But more
investigation work is necessary.

To unblock nightly release, revert the change.

The only remaining change from go.dev/cl/380175 is to switch
from repository_dispatch to workflow_dispatch, and
use of the Nightly environment.

Change-Id: I11bd655b875208c6001afd9fe03e511d0396d573
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/381574
Trust: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>

.github/workflows/release-nightly.yml

@@ -8,11 +8,12 @@ on:
   workflow_dispatch:   
 
 jobs:
-  build:
-    if: github.ref == 'refs/heads/master'
+  release:
+    if: github.ref == 'refs/heads/master' && github.repository == 'golang/vscode-go'
 
-    name: Build Nightly
+    name: Release Nightly
     runs-on: ubuntu-latest
+    environment: nightly
     timeout-minutes: 20
 
     steps:
@@ -58,14 +59,8 @@ jobs:
           CODE_VERSION: 'insiders'
           VSCODEGO_BEFORE_RELEASE_TESTS: true
 
-  publish:
-    if: github.ref == 'refs/heads/master' && github.repository == 'golang/vscode-go'
-
-    needs: [build]
-    runs-on: ubuntu-latest
-    environment: nightly
-    steps:
       - name: Publish
+        if: github.ref == 'refs/heads/master' && github.repository == 'golang/vscode-go'
         uses: lannonbr/vsce-action@0f3391ee0477b08fae949eb0a875e91e6d20b075
         with:
           args: "publish -p $VSCE_TOKEN"