clean-up "nolint" comments, remove unused ones

- fix "nolint" comments to be in the correct format (`//nolint:<linters>[,<linter>`
  no leading space, required colon (`:`) and linters.
- remove "nolint" comments for errcheck, which is disabled in our config.
- remove "nolint" comments that were no longer needed (nolintlint).
- where known, add a comment describing why a "nolint" was applied.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

pkg/runtimeoptions/v1/doc.go

@@ -14,4 +14,4 @@
    limitations under the License.
 */
 
-package runtimeoptions_v1 //nolint
+package runtimeoptions_v1 //nolint:revive // Ignore var-naming: don't use an underscore in package name (revive)