Bump http to 2993ea5dff5ffb066b4a35c707e7a2b8dcfa17c2

Changes:
```
> git log --format="%C(auto) %h %s" 2c9b418..2993ea5
 https://dart.googlesource.com/http.git/+/2993ea5 Implement the ability to run a particular Client implementation in a Zone (#697)
 https://dart.googlesource.com/http.git/+/fa0af10 Fix head, get, post, etc. links in Client docs (#703)
 https://dart.googlesource.com/http.git/+/6b3e3f3 Use spawnHybrid for the stub server (#700)
 https://dart.googlesource.com/http.git/+/74a4371 Separate the `post` description for "String" (#695)
 https://dart.googlesource.com/http.git/+/87d4379 Switch from homepage to repository in pubspec  (#687)

```

Diff: https://dart.googlesource.com/http.git/+/2c9b418f5086f999c150d18172d2eec1f963de7b~..2993ea5dff5ffb066b4a35c707e7a2b8dcfa17c2/
Change-Id: I121641dc9f75d8ccb6d62fd9baec20b951bdbcde
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/246761
Commit-Queue: Devon Carew <devoncarew@google.com>
Reviewed-by: Nate Bosch <nbosch@google.com>
diff --git a/DEPS b/DEPS
index 797f60b..8f39c5f 100644
--- a/DEPS
+++ b/DEPS
@@ -116,7 +116,7 @@
   "http_io_rev": "405fc79233b4a3d4bb079ebf438bb2caf2f49355",
   "http_multi_server_rev": "35a3b947256768426090e3b1f5132e4fc23c175d",
   "http_parser_rev": "9126ee04e77fd8e4e2e6435b503ee4dd708d7ddc",
-  "http_rev": "2c9b418f5086f999c150d18172d2eec1f963de7b",
+  "http_rev": "2993ea5dff5ffb066b4a35c707e7a2b8dcfa17c2",
   "icu_rev": "81d656878ec611cb0b42d52c82e9dae93920d9ba",
   "intl_rev": "9145f308f1458f37630a1ffce3b7d3b471ebbc56",
   "jinja2_rev": "2222b31554f03e62600cd7e383376a7c187967a1",