docs: clarify krel install locations + go install

[singh1203]

What type of PR is this?

/kind documentation

What this PR does / why we need it:

Current docs list methods without explaining where binaries land, leading to confusion ("where's my krel?").

So this Pull Request clarifies krelinstallation locations (repo-local ./bin/krel vs Go bin) and recommends go install + PATH setup as the happy path.

Which issue(s) this PR fixes:

None

Special notes for your reviewer:

• Docs-only, no behavior changes

Does this PR introduce a user-facing change?

Clarified `krel` installation documentation to show where binaries are installed for each method.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: singh1203
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