NavigationController: revise a wrong comment on NO_RELOAD
NavigationController: revise a wrong comment on NO_RELOAD

The comment was revised recently, but actually, it wasn't accurate.
This change clarifies ReloadType NO_RELOAD behaviors.

BUG=n/a

Review URL: https://codereview.chromium.org/1826203005

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#383484}

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