turn variables off in no-use-before-define rule

When set to false, "the rule ignores a reference if the declaration
is in an upper scope, while still reporting the reference if it's
in the same scope as the declaration."
https://eslint.org/docs/latest/rules/no-use-before-define

test plan:
  - existing tests pass

flag=none

Change-Id: I3b4d071d97e713f4f02842ac9a684080340e71f8
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/316676
Reviewed-by: Kai Bjorkman <kbjorkman@instructure.com>
Reviewed-by: Cameron Ray <cameron.ray@instructure.com>
QA-Review: Kai Bjorkman <kbjorkman@instructure.com>
Product-Review: Cameron Ray <cameron.ray@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>

.eslintrc.js

@@ -96,6 +96,7 @@ module.exports = {
       {
         functions: false,
         classes: false,
+        variables: false,
       },
     ],
     'no-useless-escape': 'off',