Clean KernelInterface docblocks

- Fixed questionable grammar
- Added missing periods to make it consistent
minor #10525 [HttpKernel] Clean KernelInterface docblocks (sbward)

This PR was submitted for the 2.3-dev branch but it was merged into the 2.3 branch instead (closes #10525).

Discussion
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[HttpKernel] Clean KernelInterface docblocks

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

- Fixed questionable grammar
- Added missing periods to make it consistent

Commits
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4b1f050 Clean KernelInterface docblocks