[dependabot] Teach it to not suggest hsqldb 2.6.0+ as that requires jdk 11

Author: hazendaz

.github/dependabot.yml

@@ -21,3 +21,7 @@ updates:
   schedule:
     interval: daily
   open-pull-requests-limit: 10
+  ignore:
+  - dependency-name: org.hsqldb:hsqldb
+    versions:
+    - ">= 2.6.0"