Bug 1875027 - Remove deprecated ESLint rule no-return-await. r=mossop

Eslint has now deprecated the rule.

Depends on D198777

Differential Revision: https://phabricator.services.mozilla.com/D198778

.eslintrc.js

@@ -414,7 +414,6 @@ module.exports = {
         "no-new-wrappers": "off",
         "no-redeclare": "off",
         "no-restricted-globals": "off",
-        "no-return-await": "off",
         "no-sequences": "off",
         "no-throw-literal": "off",
         "no-useless-concat": "off",
@@ -479,7 +478,6 @@ module.exports = {
         "no-new-object": "off",
         "no-new-wrappers": "off",
         "no-redeclare": "off",
-        "no-return-await": "off",
         "no-restricted-globals": "off",
         "no-shadow": "off",
         "no-sparse-arrays": "off",

tools/lint/eslint/eslint-plugin-mozilla/lib/configs/recommended.js

@@ -293,9 +293,6 @@ module.exports = {
     // Disallow use of event global.
     "no-restricted-globals": ["error", "event"],
 
-    // Disallows unnecessary `return await ...`.
-    "no-return-await": "error",
-
     // No unnecessary comparisons
     "no-self-compare": "error",