Update immutable to v5.1.5 (#2122)

* Update immutable to v5.1.5

* Update `immutable` imports from default to namespace

Author: Goodwine

js-api-spec/setup.ts

@@ -2,7 +2,7 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
-import immutable from 'immutable';
+import * as immutable from 'immutable';
 import * as sass from 'sass';
 import * as util from 'util';
 import type {URL} from 'url';

package-lock.json

@@ -44,7 +44,7 @@
     "file-lines-count": "^1.0.1",
     "fs-extra": "^10.0.0",
     "gts": "^3.1.0",
-    "immutable": "^4.0.0",
+    "immutable": "^5.1.5",
     "intercept-stdout": "^0.1.2",
     "jasmine": "^4.6.0",
     "jasmine-expect": "^5.0.0",