K8SPG-604: fix custom-extensions for non 16 PG version

[eleo007]

CHANGE DESCRIPTION

Problem:
Custom-extensions test fails when not PG 16 version is used

Cause:
initContainers.name in tests contains PG16 version hardcoded.

Solution:
Remove entries from tests that have hardcoded version

CHECKLIST

Jira

• Is the Jira ticket created and referenced properly?
• Does the Jira ticket have the proper statuses for documentation (Needs Doc) and QA (Needs QA)?
• Does the Jira ticket link to the proper milestone (Fix Version field)?

Tests

• Is an E2E test/test case added for the new feature/change?
• Are unit tests added where appropriate?

Config/Logging/Testability

• Are all needed new/changed options added to default YAML files?
• Did we add proper logging messages for operator actions?
• Did we ensure compatibility with the previous version or cluster upgrade process?
• Does the change support oldest and newest supported PG version?
• Does the change support oldest and newest supported Kubernetes version?