Increase frequency of canary runs to 4xDay (#41056)

We have not seen a significant increase in a number of FT runners
used when we run Canary builds 2x day, switching it to 4x day will
speed up constraints and cache refresh as well as will allow to
detect the root cause of main problems more accurately and will
better handle flaky cases.

.github/workflows/ci.yml

@@ -19,7 +19,7 @@
 name: Tests
 on:  # yamllint disable-line rule:truthy
   schedule:
-    - cron: '28 7,15 * * *'
+    - cron: '28 1,7,13,19 * * *'
   push:
     branches: ['v[0-9]+-[0-9]+-test']
   pull_request: