dependabot: ignore jetty versions >= 10

Change-Id: I9bad76f12ae2d7cc80f6c14294637973eb1d0c72
diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index daec318..3390852 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -4,3 +4,12 @@
     directory: "/"
     schedule:
       interval: "daily"
+    ignore:
+      # Jetty >= 10 requires JDK 11
+      - dependency-name: "org.eclipse.jetty:jetty-server"
+        versions:
+          - ">= 10.0.0"
+      - dependency-name: "org.eclipse.jetty:jetty-servlet"
+        versions:
+          - ">= 10.0.0"
+    open-pull-requests-limit: 50