[ez] Don't output the command when running test262

Currently yarn prints out the command prior to executing it which makes test 
output for test262 very verbose

compiler/forget/package.json

@@ -14,7 +14,7 @@
     "playground": "cd packages/playground && yarn && yarn dev",
     "test": "yarn build && jest",
     "ts:analyze-trace": "scripts/ts-analyze-trace.sh",
-    "test262": "yarn test262-harness --preprocessor=scripts/test262-preprocessor.js",
+    "test262": "yarn run --silent test262-harness --preprocessor=scripts/test262-preprocessor.js",
     "test262:all": "scripts/test262-all.sh"
   },
   "repository": {

compiler/forget/scripts/test262-all.sh

@@ -7,5 +7,5 @@ set -eo pipefail
 
 for dir in test262/test/*;
 do
-  yarn test262 $dir/**/*.js;
+  yarn run --silent test262 $dir/**/*.js;
 done