Wait for dist-tag updates to finish

The logs from the `update-next-tags` script indicate that things
aren't correctly being waited on. Some logs are missing entirely.
Some packages don't get their appropriate update. This change
should at least get us the logs if it doesn't fix the issue itself.

scripts/update-next-tags.mjs

@@ -1,10 +1,13 @@
 // @ts-check
 import { exec } from "child_process";
+import { promisify } from "util";
 import { readFileSync } from "fs";
 import fetch from "node-fetch";
 import { resolve } from "path";
 import semver from "semver";
 
+const asyncExec = promisify(exec);
+
 let statusCode = 0;
 // Collect all the packages that we publish
 const workspaces = JSON.parse(
@@ -37,14 +40,14 @@ await Promise.all(
       const command = `npm dist-tag add ${pkg}@${mostRecentVersion} next`;
       if (nextVersion !== mostRecentVersion) {
         console.log(`\`next\` tag is behind, updating...`);
-        exec(command, (e) => {
-          if (e) {
-            console.error(e);
-            throw e;
-          } else {
-            console.log("`next` tag updated successfully!");
-          }
-        });
+        try {
+          const { stdout, stderr } = await asyncExec(command)
+          if (stderr) console.error(stderr);
+          if (stdout) console.log(stdout);
+        } catch (e) {
+          console.error(e);
+          throw e;
+        }
       } else {
         console.log(
           "No action needed, `next` tag is pointed to most recent version"