eslintrc: enable no-test-import-export rule (#1989)
eslintrc: enable no-test-import-export rule (#1989)

Due to how qunit unloads a test module, importing a test file will cause
any modules and tests within the file to be executed every time it gets
loaded.

The no-test-import-export eslint rule will help us avoid this by
checking for any imports or exports from *-test.js files.

As we don't have any outstanding issues of this nature, let's go ahead
and re-enable the rule so that the linter will help us avoid adding any
going forward.
emberjs/ember-inspector,emberjs/ember-inspector