fix: Remove @ember/string dependency

- Not needed / used anywhere
- Fixes #146

Author: MichalBryxi

package.json

@@ -42,7 +42,6 @@
     "@commitlint/cli": "^16.2.3",
     "@commitlint/config-conventional": "^16.2.1",
     "@ember/optional-features": "^2.0.0",
-    "@ember/string": "^3.1.1",
     "@ember/test-helpers": "^2.6.0",
     "@ember/test-waiters": "~3.0.1",
     "@embroider/macros": "^1.0.0",

yarn.lock

@@ -1163,13 +1163,6 @@
     mkdirp "^1.0.4"
     silent-error "^1.1.1"
 
-"@ember/string@^3.1.1":
-  version "3.1.1"
-  resolved "https://registry.yarnpkg.com/@ember/string/-/string-3.1.1.tgz#0a5ac0d1e4925259e41d5c8d55ef616117d47ff0"
-  integrity sha512-UbXJ+k3QOrYN4SRPHgXCqYIJ+yWWUg1+vr0H4DhdQPTy8LJfyqwZ2tc5uqpSSnEXE+/1KopHBE5J8GDagAg5cg==
-  dependencies:
-    ember-cli-babel "^7.26.6"
-
 "@ember/test-helpers@^2.6.0":
   version "2.7.0"
   resolved "https://registry.yarnpkg.com/@ember/test-helpers/-/test-helpers-2.7.0.tgz#d8e08b614cdd5eac647689d655e78e1de725f474"