Remove more yarn remnants

Author: Robert Jackson

.github/workflows/build.yml

@@ -44,7 +44,7 @@ jobs:
       - name: Lint
         run: npm run lint
       - name: Build
-        run: yarn ember build --environment test
+        run: npx ember build --environment test
       - name: Run test
         # Due to a bug in ember-cli, running `ember test` with `--path` doesn't set `EMBER_ENV=test`
         # See https://github.com/ember-cli/ember-cli/issues/8922

CONTRIBUTING.md

@@ -4,12 +4,12 @@
 
 * `git clone <repository-url>`
 * `cd ember-cli-head`
-* `yarn install`
+* `npm ci`
 
 ## Linting
 
-* `yarn lint`
-* `yarn lint:fix`
+* `npm run lint`
+* `npm run lint:fix`
 
 ## Running tests
 

tests/dummy/config/ember-cli-update.json

@@ -11,7 +11,6 @@
           "codemodsSource": "ember-addon-codemods-manifest@1",
           "isBaseBlueprint": true,
           "options": [
-            "--yarn",
             "--no-welcome"
           ]
         }