Execute multi-Java test suite on Wednesday and Sunday only

Used to be every day. It may be too much for our GHA quota,
so we reduce the frequency. It should do the job as well.

(cherry picked from commit 84ddee0)

Author: acogoluegnes

.github/workflows/test-3.11-alpha.yml

@@ -2,7 +2,7 @@ name: Test against RabbitMQ 3.11 alpha
 
 on:
   schedule:
-    - cron: '0 4 * * *'
+    - cron: '0 4 ? * SUN,WED'
   pull_request:
     branches:
       - 5.x.x-stable

.github/workflows/test-native-image.yml

@@ -2,7 +2,7 @@ name: Test GraalVM native image
 
 on:
   schedule:
-    - cron: '0 4 * * *'
+    - cron: '0 4 ? * SUN,WED'
   workflow_dispatch:
 
 env:

.github/workflows/test-supported-java-versions-5.x.yml

@@ -2,7 +2,7 @@ name: Test against supported Java versions (5.x)
 
 on:
   schedule:
-    - cron:  '0 4 * * *'
+    - cron: '0 4 ? * SUN,WED'
   workflow_dispatch:
 
 env:

.github/workflows/test-supported-java-versions-main.yml

@@ -2,7 +2,7 @@ name: Test against supported Java versions (main)
 
 on:
   schedule:
-    - cron:  '0 4 * * *'
+    - cron: '0 4 ? * SUN,WED'
   workflow_dispatch:
 
 env: