Merge pull request atom#21928 from atom/fix-dependency-bump-failure

Fixes dependency bump script

Author: darangi

script/lib/update-dependency/git.js

@@ -19,10 +19,7 @@ const git = (git, repositoryRootPath) => {
   }
   return {
     switchToMaster: async function() {
-      const { current } = await git.branch();
-      if (current !== 'master') {
-        await git.checkout('master');
-      }
+      await git.checkout('origin/master');
     },
     makeBranch: async function(dependency) {
       const newBranch = `${dependency.moduleName}-${dependency.latest}`;