Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[x] Bug fix (template)
[ ] New rule (template)
[ ] Changes an existing rule (template)
[ ] Add autofix to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

Fixes types for the patterns option of the no-restricted-imports rule.

What changes did you make? (Give an overview)

• A patterns object should be valid without either of importNames, importNamePattern, allowImportNames or allowImportNamePattern specified. For example, "no-restricted-imports": [2, { patterns: [{ group: ["foo"] }] }] was invalid before this change.
• importNames and importNamePattern can be specified in the same object. For example, "no-restricted-imports": [2, { patterns: [{ group: ["foo"], importNames: ["bar"], importNamePattern: "baz" }] }] was invalid before this change.
• Mixing strings and objects is not allowed. For example, "no-restricted-imports": [2, { patterns: [{ group: ["foo"], importNames: ["bar"]}, "bar"] }] was valid before this change.

Is there anything you'd like reviewers to focus on?