test(@angular/cli): disable NPM 7 with Node v10 test

NPM 7 doesn't support Node v10, so this test will always fail.

(cherry picked from commit 3230d0f)

Author: dgp1130

tests/legacy-cli/e2e/tests/misc/npm-7.ts

@@ -10,6 +10,11 @@ export default async function() {
     return;
   }
 
+  // NPM 7 doesn't support Node v10.
+  if (process.version.startsWith('v10')) {
+    return;
+  }
+
   const currentDirectory = process.cwd();
   try {
     // Install version >=7.5.6