Bump merge from 1.2.0 to 1.2.1 in /generator-exercise

Bumps [merge](https://github.com/yeikos/js.merge) from 1.2.0 to 1.2.1.
- [Release notes](https://github.com/yeikos/js.merge/releases)
- [Commits](https://github.com/yeikos/js.merge/compare/v1.2.0...v1.2.1)

Signed-off-by: dependabot[bot] <support@github.com>

generator-exercise/package-lock.json

@@ -3210,9 +3210,9 @@
       }
     },
     "merge": {
-      "version": "1.2.0",
+      "version": "1.2.1",
-      "resolved": "https://registry.npmjs.org/merge/-/merge-1.2.0.tgz",
+      "resolved": "https://registry.npmjs.org/merge/-/merge-1.2.1.tgz",
-      "integrity": "sha1-dTHjnUlJwoGma4xabgJl6LBYlNo=",
+      "integrity": "sha512-VjFo4P5Whtj4vsLzsYBu5ayHhoHJ0UqNm7ibvShmbmoz7tGi0vXaoJbGdB+GmDMLUdg8DpQXEIeVDAe8MaABvQ==",
       "dev": true
     },
     "micromatch": {