Fix build of readonly plugin for stable-3.9 and older

- Due to https://gerrit-review.googlesource.com/c/gerrit/+/400622
  stable-3.9 and older didn't compile against Gerrit master anymore.
- Added the missing stable-3.8 branch
- Add build for stable-3.10
- Remove the 3.7 build since its EOL now.

Change-Id: Iccb75e4dd552d9cac1cb2d2c3bcb099d3e47c504
diff --git a/jenkins/gerrit-bazel-plugin-readonly.yaml b/jenkins/gerrit-bazel-plugin-readonly.yaml
index bd7ae86..983e665 100644
--- a/jenkins/gerrit-bazel-plugin-readonly.yaml
+++ b/jenkins/gerrit-bazel-plugin-readonly.yaml
@@ -5,8 +5,9 @@
           branch:
             - master
           gerrit-branch:
-            - stable-3.8
-            - stable-3.7
+            - stable-3.10
       - 'plugin-{name}-bazel-{branch}':
           branch:
             - master
+            - stable-3.9
+            - stable-3.8