use upstream/version-2-0 of Nim in CI (#6277)

.github/workflows/ci.yml

@@ -35,7 +35,7 @@ jobs:
             cpu: amd64
           - os: windows
             cpu: amd64
-        branch: [~, upstream/version-1-6, v2.0.4]
+        branch: [~, upstream/version-1-6, upstream/version-2-0]
         exclude:
           - target:
               os: macos
@@ -49,7 +49,7 @@ jobs:
         include:
           - branch: upstream/version-1-6
             branch-short: version-1-6
-          - branch: v2.0.4
+          - branch: upstream/version-2-0
             branch-short: version-2-0
             nimflags-extra: --mm:refc
           - target:

ci/Jenkinsfile

@@ -183,5 +183,5 @@ def getAgentLabel() {
 }
 
 def nimCommitForJob() {
-  return JOB_NAME.contains('nimv2') ? 'v2.0.4' : ''
+  return JOB_NAME.contains('nimv2') ? 'upstream/version-2-0' : ''
 }