Bump pub to 1e3c17ea871e6a80c720aa998f37cbd3913bc287

Changes:
```
> git log --format="%C(auto) %h %s" 6068f47..1e3c17e
 https://dart.googlesource.com/pub.git/+/1e3c17ea dependency_services: use revisions as versions for git deps. (#3383)
 https://dart.googlesource.com/pub.git/+/9ecdd6b1 show discontinued in pub outdated (#3399)
 https://dart.googlesource.com/pub.git/+/c8fdf231 Bump analyzer from 3.4.1 to 4.0.0 (#3412)

```

Diff: https://dart.googlesource.com/pub.git/+/6068f47c264ef790e16411b31b2c94ad6beb1ab6~..1e3c17ea871e6a80c720aa998f37cbd3913bc287/
Change-Id: Idb9484e36d03001039e9f7e5447c659b85bd093f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/244621
Reviewed-by: Jonas Jensen <jonasfj@google.com>
Commit-Queue: Sigurd Meldgaard <sigurdm@google.com>

Author: sigurdm

CHANGELOG.md

@@ -28,6 +28,10 @@ Updated the Linter to `1.23.0`, which includes changes that
 - fixes `unnecessary_null_checks` to properly handle map
   literal entries.
 
+#### Pub
+
+* `dart pub outdated` now shows which of your dependencies are discontinued.
+
 ## 2.17.0
 
 ### Language

DEPS

@@ -138,7 +138,7 @@ vars = {
   "pool_rev": "7abe634002a1ba8a0928eded086062f1307ccfae",
   "process_rev": "56ece43b53b64c63ae51ec184b76bd5360c28d0b",
   "protobuf_rev": "c1eb6cb51af39ccbaa1a8e19349546586a5c8e31",
-  "pub_rev": "6068f47c264ef790e16411b31b2c94ad6beb1ab6",
+  "pub_rev": "1e3c17ea871e6a80c720aa998f37cbd3913bc287",
   "pub_semver_rev": "ea6c54019948dc03042c595ce9413e17aaf7aa38",
   "root_certificates_rev": "692f6d6488af68e0121317a9c2c9eb393eb0ee50",
   "rust_revision": "b7856f695d65a8ebc846754f97d15814bcb1c244",