Build: Remove an obsolete test/.eslintrc.json file

The file was erroneously left in during the migration to the flat config.

Closes gh-2340
Ref gh-2336

tests/.eslintrc.json

@@ -1,26 +0,0 @@
-{
-	"parserOptions": {
-		"ecmaVersion": 5
-	},
-
-	"env": {
-		"browser": true,
-		"jquery": true,
-		"node": false
-	},
-
-	"rules": {
-		// Too many violations:
-		"max-len": "off",
-		"no-unused-vars": "off",
-		"strict": "off" // ideally, `[ "error", "function" ]`
-	},
-
-	"globals": {
-		"define": false,
-		"Globalize": false,
-		"QUnit": false,
-		"require": true,
-		"requirejs": true
-	}
-}