GEODE-10569: Replace 1.15.2 with 1.15.3 as old version

Replace 1.15.2 with 1.15.3 in old versions on support/1.15
to enable rolling upgrade tests from 1.15.3

The serialization version has not changed between 1.15.2 and 1.15.3,
so there should be no need to keep both

Author: JinwooHwang

settings.gradle

@@ -110,7 +110,8 @@ include 'geode-server-all'
  '1.13.8',
  '1.14.0', // Include for SSL protocol configuration changes in 1.14.0
  '1.14.4',
- '1.15.1'].each {
+ '1.15.1',
+ '1.15.3'].each {
   include 'geode-old-versions:'.concat(it)
 }