Add test job for stable-3.10

Change-Id: I1eb0f300f3b547e6f20dbc1f4425b741147eff98

zuul.d/project.yaml

diff --git a/zuul.d/project.yaml b/zuul.d/project.yaml
index b172dad..bacd823 100644
--- a/zuul.d/project.yaml
+++ b/zuul.d/project.yaml
@@ -10,5 +10,6 @@
         - test-gerrit-build-stable-3.7
         - test-gerrit-build-stable-3.8
         - test-gerrit-build-stable-3.9
+        - test-gerrit-build-stable-3.10
         - test-gitiles-build-master
         - test-install-build-essential

zuul.d/test-jobs.yaml

diff --git a/zuul.d/test-jobs.yaml b/zuul.d/test-jobs.yaml
index 4b69d1f..503bb26 100644
--- a/zuul.d/test-jobs.yaml
+++ b/zuul.d/test-jobs.yaml
@@ -91,6 +91,11 @@
     override-checkout: stable-3.9
 
 - job:
+    name: test-gerrit-build-stable-3.10
+    parent: test-gerrit-build-master
+    override-checkout: stable-3.10
+
+- job:
     name: test-gitiles-build-master
     parent: gitiles-build
     files: