docs: Update PR template for new metrics

[onasser1]

What this PR does / why we need it:
Update PULL_REQUEST_TEMPLATE / docs enhancement
How does this change affect the cardinality of KSM: (increases, decreases or does not change cardinality)
Does not change cardinality
Which issue(s) this PR fixes: (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged)
Fixes #2734

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[onasser1]

@CatherineF-dev can something like this be appropriate?

[onasser1]

@rexagod can I get hint here? Thanks 🥳

[rexagod]

/triage accepted
/assign @CatherineF-dev

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