Revert explicit peerDependencies contracts

I originally [thought][1] these `peerDependencies` were not breaking
because users would be able to opt into them. Unfortunately, this is
[not the case][2]: users on Ember 3.28 will have an older copy of these
dependencies, so correctly validating these breaks consumers.

[1]: #995 (comment)
[2]: #997 (comment)

We should bundle these into a v7.0.0 when we drop Node 14 and Ember
3.28, presumably in ~April 2023.

Fixes #997

package.json

@@ -55,6 +55,7 @@
     "@glimmer/interfaces": "^0.84.2",
     "@glimmer/reference": "^0.84.2",
     "@tsconfig/ember": "^1.1.0",
+    "@types/ember-resolver": "^5.0.13",
     "@types/qunit": "^2.19.3",
     "@types/rsvp": "^4.0.4",
     "ember-angle-bracket-invocation-polyfill": "^3.0.2",
@@ -85,36 +86,9 @@
     "webpack": "^5.75.0"
   },
   "peerDependencies": {
-    "@ember/test-helpers": "^2.4.0",
-    "@glimmer/interfaces": "^0.84.2",
-    "@glimmer/reference": "^0.84.2",
-    "@types/ember-resolver": "^5.0.13",
-    "@types/ember__test": "^4.0.1",
-    "@types/ember__test-helpers": "^2.8.2",
-    "@types/rsvp": "^4.0.4",
     "ember-source": "^3.28 || ^4.0",
     "qunit": "^2.13.0"
   },
-  "peerDependenciesMeta": {
-    "@types/ember__test": {
-      "optional": true
-    },
-    "@types/ember-resolver": {
-      "optional": true
-    },
-    "@types/ember__test-helpers": {
-      "optional": true
-    },
-    "@types/rsvp": {
-      "optional": true
-    },
-    "@glimmer/interfaces": {
-      "optional": true
-    },
-    "@glimmer/reference": {
-      "optional": true
-    }
-  },
   "engines": {
     "node": "14.* || 16.* || >= 18"
   },