tools: enable no-cond-assign-ESLint rule

no-cond-assign is one of the few ESLint recommended rules that we have turned off. This change enables the rule.

Author: Trott

.eslintrc.js

@@ -297,7 +297,6 @@ module.exports = {
  'valid-typeof': ['error', { requireStringLiterals: true }],
 
  // ESLint recommended rules that we disable
- 'no-cond-assign': 'off',
  'no-empty': 'off',
  'no-inner-declarations': 'off',
  'no-prototype-builtins': 'off',