Bump pub to ec35d46261b610e558dfd0d8525ca3fc8387b4b7

Changes:
```
> git log --format="%C(auto) %h %s" ac7db6c..ec35d46
 https://dart.googlesource.com/pub.git/+/ec35d462 Fix null-safety warning in dart.dart (#3514)
 https://dart.googlesource.com/pub.git/+/7d30cf0b Allow pubspec key 'funding' (#3529)
 https://dart.googlesource.com/pub.git/+/8ff63a8e Fix remaining usages of path.prettyUri on git uris (#3524)
 https://dart.googlesource.com/pub.git/+/bc32a30e Fix typo "exitcode" (#3511)

```

Diff: https://dart.googlesource.com/pub.git/+/ac7db6c07318efa4a8712110275eaf70f96a6d00~..ec35d46261b610e558dfd0d8525ca3fc8387b4b7/
Change-Id: I535f4fab8940ee8400ef75369d35fb4c1ee3adab
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/255990
Reviewed-by: Sarah Zakarias <zarah@google.com>
Commit-Queue: Sigurd Meldgaard <sigurdm@google.com>

CHANGELOG.md

@@ -106,6 +106,7 @@ Updated the Linter to `1.27.0`, which includes changes that
 
 - Remove remaining support for `.packages` files. The flag
   `--legacy-packages-file` is no longer supported.
+- Support a new field `funding` in pubspec.yaml.
 
 #### dart2js
 

DEPS

@@ -136,7 +136,7 @@ vars = {
   "ply_rev": "604b32590ffad5cbb82e4afef1d305512d06ae93",
   "pool_rev": "fa84ddd0e39f45bf3f09dcc5d6b9fbdda7820fef",
   "protobuf_rev": "8337a7910fef805214e5aae35a98abd481d87a18",
-  "pub_rev": "ac7db6c07318efa4a8712110275eaf70f96a6d00", # manually rev'd
+  "pub_rev": "ec35d46261b610e558dfd0d8525ca3fc8387b4b7", # manually rev'd
   "pub_semver_rev": "9fd28757ba45961ac5449e0f2b0020670e921475",
   "root_certificates_rev": "692f6d6488af68e0121317a9c2c9eb393eb0ee50",
   "shelf_rev": "0965d864d0e6c66d5bb6daece400e80484640bd5",