Revert "build(vercel): Migrate from "now" to "vercel" (#20561)" (#20754)

This reverts commit 5821c8b8cc076fec1dba782fba1b1b88869e36cb.

OK, I was fed bad information and migrating to vercel config did break things. Previously, Vercel deploys are successfully deployed, but the ignore file does not seem to be respected. This means that the app that is successfully deployed is incomplete.

webpack.config.js

@@ -26,7 +26,7 @@ const IS_PRODUCTION = env.NODE_ENV === 'production';
 const IS_TEST = env.NODE_ENV === 'test' || env.TEST_SUITE;
 const IS_STORYBOOK = env.STORYBOOK_BUILD === '1';
 const IS_CI = !!env.CI || !!env.TRAVIS;
-const IS_DEPLOY_PREVIEW = !!env.VERCEL_GITHUB_DEPLOYMENT;
+const IS_DEPLOY_PREVIEW = !!env.NOW_GITHUB_DEPLOYMENT;
 const IS_UI_DEV_ONLY = !!env.SENTRY_UI_DEV_ONLY;
 const DEV_MODE = !(IS_PRODUCTION || IS_CI);
 const WEBPACK_MODE = IS_PRODUCTION ? 'production' : 'development';
@@ -53,10 +53,10 @@ const SHOULD_HOT_MODULE_RELOAD = DEV_MODE && !!env.SENTRY_UI_HOT_RELOAD;
 // Deploy previews are built using zeit. We can check if we're in zeit's
 // build process by checking the existence of the PULL_REQUEST env var.
 const DEPLOY_PREVIEW_CONFIG = IS_DEPLOY_PREVIEW && {
-  branch: env.VERCEL_GITHUB_COMMIT_REF,
-  commitSha: env.VERCEL_GITHUB_COMMIT_SHA,
-  githubOrg: env.VERCEL_GITHUB_COMMIT_ORG,
-  githubRepo: env.VERCEL_GITHUB_COMMIT_REPO,
+  branch: env.NOW_GITHUB_COMMIT_REF,
+  commitSha: env.NOW_GITHUB_COMMIT_SHA,
+  githubOrg: env.NOW_GITHUB_COMMIT_ORG,
+  githubRepo: env.NOW_GITHUB_COMMIT_REPO,
 };
 
 // When deploy previews are enabled always enable experimental SPA mode --