Fixing Issues with RDS Compositions and Example.

[elamaran11]

What does this PR do?

This PR is to fix the issues with RDS Compositions and examples :

1. Engine version is fixed to update the depracated version. Depracated version no longer works and MR resource fails.
2. Fixing issue with password auto generation which is not working. Password auto generation is no longer supported and MOR resource fails.
3. Adding right namespace to passwords with password snippet for postgres example

Motivation

Make RDS Compositions work.

More

• Yes, I have tested the PR using my local account setup (Provide any test evidence report under Additional Notes)

• Yes, I have added a new example under examples to support my PR

• Yes, I have updated the docs for this feature

• Yes, I have linked to an issue or feature request (applicable to PRs that solves a bug or a feature request)

Note:

• Not all the PRs require examples and docs
• We prefer small, well tested pull requests. Please ensure your pull requests are self-contained, and commits are squashed

For Moderators

• E2E Test successfully complete before merge?

Additional Notes

[elamaran11]

@candonov Please merge this PR>

[candonov]

lgtm