Bump pub to 35681b0126a1fb48bf2062dd09f74296715402c2

The pub client still won't send analytics with this PR. (This will be
enabled in a follow-up).

Changes:
```
> git log --format="%C(auto) %h %s" 0764437..35681b0
 https://dart.googlesource.com/pub.git/+/35681b01 Analytics (#2778)
 https://dart.googlesource.com/pub.git/+/9c65d31c Accept 'platforms' property in pubspec.yaml (#3176)
 https://dart.googlesource.com/pub.git/+/1af0de54 Accept 'screenshots' property in pubspec.yaml (#3174)
 https://dart.googlesource.com/pub.git/+/19045b95 Tests related to token authentication (#3147)
 https://dart.googlesource.com/pub.git/+/f36da07f Use applicationConfigHome from package:cli_util (#3164)

```

Diff: https://dart.googlesource.com/pub.git/+/0764437088fd58eb7af779ecef66bab40dfcf2e9~..35681b0126a1fb48bf2062dd09f74296715402c2/
Change-Id: I7313f3125934aba3473b2725074bfc7fd92e25e4
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/217004
Reviewed-by: Jonas Jensen <[email protected]>
Commit-Queue: Sigurd Meldgaard <[email protected]>

Author: sigurdm

DEPS

@@ -139,7 +139,7 @@ vars = {
   "pool_rev": "7abe634002a1ba8a0928eded086062f1307ccfae",
   "process_rev": "56ece43b53b64c63ae51ec184b76bd5360c28d0b",
   "protobuf_rev": "c1eb6cb51af39ccbaa1a8e19349546586a5c8e31",
-  "pub_rev": "0764437088fd58eb7af779ecef66bab40dfcf2e9",
+  "pub_rev": "35681b0126a1fb48bf2062dd09f74296715402c2",
   "pub_semver_rev": "a43ad72fb6b7869607581b5fedcb186d1e74276a",
   "root_certificates_rev": "692f6d6488af68e0121317a9c2c9eb393eb0ee50",
   "rust_revision": "b7856f695d65a8ebc846754f97d15814bcb1c244",