Update Resource.v1alpha1.schema.json

[hpractv]

Remove the mention of metadata.instances because it's not supported.

Summary of PR changes

PR Requirements

• For major, minor, or breaking changes, at least one of the commit messages contains the appropriate +semver: keywords.
  • See the Incrementing the Version section of the repository's README.md for more details.
• The action code does not contain sensitive information.

NOTE: If the repo's workflow could not automatically update the README.md, it should be updated manually with the next version. For javascript actions, if the repo's workflow could not automatically recompile the action it should also be updated manually as part of the PR.

[github-actions]

Before this PR can be merged, the following item(s) should be addressed to comply with the action's Contributing Guidelines.

• Please update the action's version in the Usage Examples section of README.md. Each instance of this action should be updated to:
  uses: im-open/[email protected]
• Please ensure the action has been recompiled by running the following command from the root of the repository:
  npm run build

[github-actions]

Before this PR can be merged, the following item(s) should be addressed to comply with the action's Contributing Guidelines.

• Please ensure the action has been recompiled by running the following command from the root of the repository:
  npm run build

[github-actions]

The action's Contributing Guidelines have been met:

• The action's version in the Usage Examples section of README.md has been updated to @v1.0.5
• The action has been recompiled (if needed) by running the build command from the root of the repository