[Ops] Fix @kbn/imports/no_unused_imports rule (elastic#164870)

## Summary
@jloleysens reported that ESLint breaks (probably in IDEs only) because
of this bug. When there's an unused import, linting stops for the whole
file.

By adding this flag, it no longer breaks on my machine, however,
auto-fixing still doesn't work from the CLI. The IDE auto-fixes because
it also recognizes it as a non-unsed variable.

- add `meta.hasSuggestions` to `@kbn/imports/no_unused_imports` prevent
ESLint from breaking

(cherry picked from commit d8d355d)

packages/kbn-eslint-plugin-imports/src/rules/no_unused_imports.ts

@@ -78,6 +78,7 @@ function isTsOrEslintIgnore(comment: Comment) {
 
 export const NoUnusedImportsRule: Rule.RuleModule = {
   meta: {
+    hasSuggestions: true,
     fixable: 'code',
     docs: {
       url: 'https://github.com/elastic/kibana/blob/main/packages/kbn-eslint-plugin-imports/README.mdx#kbnimportsno_unused_imports',