[docker/cli] Invalid contribution link in PR template

### ROOT CAUSE The issue arises because the PR template contains a broken link to a specific commit's file, which is no longer valid. The link was likely outdated due to changes in the repository's structure or the PR template's location, making it inaccessible. ### CODE FIX To resolve the issue, update the invalid link in the PR template to the official Docker contribution guidelines. **Step-by-step Explanation:** 1. **Locate the PR Template File:** - Navigate to the `.github` directory in the `docker/cli` repository. - Open the `PULL_REQUEST_TEMPLATE.md` file. 2. **Identify the Invalid Link:** - Find the line(s) containing the link `https://github.com/docker/cli/blob/903e9b342650ec6f5bc66681cb901361754fc67a/.github/PULL_REQUEST_TEMPLATE.md?plain=1#L7-L8`. 3. **Replace the Link:** - Remove the old link and replace it with `https://docs.docker.com/contribute/`. 4. **Commit the Change:** - Save the changes and commit them with a message like "Update invalid contribution link in PR template". **Here's the fix in the code:**

markdown
- [Contributing Guidelines](https://docs.docker.com/contribute/)


By making this change, the PR template will correctly link to Docker's official contribution guidelines, ensuring that contributors can easily find the necessary information.