Bump pub.

New commits include:
```
git log --format="%C(auto) %h %s" d159e5b9f04a7e4826b6afea7b3364d48aa0dad8..70b1a4f9229a36bac6340ec7eae2b2068baac96c
 70b1a4f9 Detect Flutter SDK location relative to Dart SDK (#3045)
 b4be5c57 Dart format with latest SDK (#3044)
 2a08832e Fix dart_tools typos (#3042)
```

Change-Id: I5d27c9545f5e13a55cf1719fe1408a88fba88c8d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/207304
Auto-Submit: Jonas Jensen <[email protected]>
Commit-Queue: William Hesse <[email protected]>
Reviewed-by: William Hesse <[email protected]>

Author: jonasfj

DEPS

@@ -141,7 +141,7 @@ vars = {
   "pool_rev": "7abe634002a1ba8a0928eded086062f1307ccfae",
   "process_rev": "56ece43b53b64c63ae51ec184b76bd5360c28d0b",
   "protobuf_rev": "0d03fd588df69e9863e2a2efc0059dee8f18d5b2",
-  "pub_rev": "d159e5b9f04a7e4826b6afea7b3364d48aa0dad8",
+  "pub_rev": "70b1a4f9229a36bac6340ec7eae2b2068baac96c",
   "pub_semver_rev": "f50d80ef10c4b2fa5f4c8878036a4d9342c0cc82",
   "resource_rev": "6b79867d0becf5395e5819a75720963b8298e9a7",
   "root_certificates_rev": "692f6d6488af68e0121317a9c2c9eb393eb0ee50",