Revert unwanted commits accidentally included from master

Commit 3e019c2 was accidentally based on a commit on the master
branch, and caused a couple of commits from master to be included
in stable-2.8:

- "Update VERSION file to 2.9-SNAPSHOT"
- "Update version to 2.9-SNAPSHOT in plugin archetype pom files"

This reverts commit 8914d9ddf0.
This reverts commit 62864b7a8a.

Change-Id: Idfd195061228274557035a0a6035bbd656ec693c

Documentation/dev-plugins.txt

@@ -38,7 +38,7 @@ plugin project.
 ----
 mvn archetype:generate -DarchetypeGroupId=com.google.gerrit \
     -DarchetypeArtifactId=gerrit-plugin-archetype \
-    -DarchetypeVersion=2.9-SNAPSHOT \
+    -DarchetypeVersion=2.8-SNAPSHOT \
     -DgroupId=com.google.gerrit \
     -DartifactId=testPlugin
 ----

Documentation/rest-api-plugins.txt

@@ -45,12 +45,12 @@ by plugin ID.
     "delete-project": {
       "kind": "gerritcodereview#plugin",
       "id": "delete-project",
-      "version": "2.9-SNAPSHOT"
+      "version": "2.8-SNAPSHOT"
     },
     "reviewers-by-blame": {
       "kind": "gerritcodereview#plugin",
       "id": "reviewers-by-blame",
-      "version": "2.9-SNAPSHOT",
+      "version": "2.8-SNAPSHOT",
       "disabled": true
     }
   }

VERSION

@@ -2,4 +2,4 @@
 # Used by :api_install and :api_deploy targets
 # when talking to the destination repository.
 #
-GERRIT_VERSION = '2.9-SNAPSHOT'
+GERRIT_VERSION = '2.8-SNAPSHOT'

gerrit-plugin-archetype/pom.xml

@@ -20,7 +20,7 @@ limitations under the License.
 
   <groupId>com.google.gerrit</groupId>
   <artifactId>gerrit-plugin-archetype</artifactId>
-  <version>2.9-SNAPSHOT</version>
+  <version>2.8-SNAPSHOT</version>
   <name>Gerrit Code Review - Plugin Archetype</name>
 
   <properties>

gerrit-plugin-gwt-archetype/pom.xml

@@ -20,7 +20,7 @@ limitations under the License.
 
   <groupId>com.google.gerrit</groupId>
   <artifactId>gerrit-plugin-gwt-archetype</artifactId>
-  <version>2.9-SNAPSHOT</version>
+  <version>2.8-SNAPSHOT</version>
   <name>Gerrit Code Review - Web Ui GWT Plugin Archetype</name>
 
   <properties>

gerrit-plugin-js-archetype/pom.xml

@@ -20,7 +20,7 @@ limitations under the License.
 
   <groupId>com.google.gerrit</groupId>
   <artifactId>gerrit-plugin-js-archetype</artifactId>
-  <version>2.9-SNAPSHOT</version>
+  <version>2.8-SNAPSHOT</version>
   <name>Gerrit Code Review - Web UI JavaScript Plugin Archetype</name>
 
   <properties>