Fix a11y file input form issue, for example when creating a Secret

[jerolimov]

Fixes:
https://issues.redhat.com/browse/ODC-6151

Analysis / Root cause:
When running some of the cypress E2E tests the import page fails with some accessibility errors.

Solution Description:
Fix a11y issues:

• Do not link to an aria-describedby element when no help text is defined.
• Add "Filename" label to the readonly field which shows the filename.

Screen shots / Gifs for design review:
UI doesn't have changed. Only a11y attributes are changed.

Before:

After:

Unit test coverage report:
Unchanged.

Test setup:

1. Open developer perspective > Add > Import from container image
2. Check accessibility errors with Firefox axe - Web Accessibility Testing extension

Browser conformance:

• Chrome
• Firefox
• Safari
• Edge

[jerolimov]

/cc @nemesis09

[nemesis09]

/lgtm

[openshift-ci]

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