Fix: Uploader UI access error

[deepsidhu85]

What does this PR do and why?

Describe in detail what your merge request does and why.

This PR updates the logic so that a user with access level uploader gets an access denied message (instead of an error message) when attempting to do an action (e.g. access a project or group that they are a member of)

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other pull requests.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Create a project and add a user with access level uploader
2. Logout and login as this user, and try to access the project. You should get an access denied error page
3. Repeat 1 and 2 for a group
4. Verify the tests pass

PR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the PR acceptance checklist for this PR.

[github-actions]

Code Metrics Report

Coverage	Test Execution Time
94.7%	11m50s

Code coverage of files in pull request scope (93.8%)

Files	Coverage
app/policies/group_policy.rb	91.4%
app/policies/project_policy.rb	96.9%

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Reported by octocov