Bump shelf to 0371a64bd3b99044ee3158bacf8813bba735a9c7

Changes:
```
> git log --format="%C(auto) %h %s" 9dab944..0371a64
 https://dart.googlesource.com/shelf.git/+/0371a64 Changed advertised server technology response header (#258)

```

Diff: https://dart.googlesource.com/shelf.git/+/9dab94469d50e89a6e4e2c0086b717bddb0bf78a~..0371a64bd3b99044ee3158bacf8813bba735a9c7/
Change-Id: I1ac864de24f5395e74816952618bcfd58d9f5d13
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/252800
Auto-Submit: Kevin Moore <[email protected]>
Reviewed-by: Devon Carew <[email protected]>
Commit-Queue: Devon Carew <[email protected]>

Author: kevmoo

DEPS

@@ -140,7 +140,7 @@ vars = {
   "pub_semver_rev": "5c0b4bfd5ca57fe16f1319c581dc8c882e9b8cb2",
   "root_certificates_rev": "692f6d6488af68e0121317a9c2c9eb393eb0ee50",
   "rust_revision": "b7856f695d65a8ebc846754f97d15814bcb1c244",
-  "shelf_rev": "9dab94469d50e89a6e4e2c0086b717bddb0bf78a",
+  "shelf_rev": "0371a64bd3b99044ee3158bacf8813bba735a9c7",
   "source_map_stack_trace_rev": "72dbf21a33293b2b8434d0a9751e36f9463981ac",
   "source_maps_rev": "e93565b43a7b6b367789de8ffba969c4ebeeb317",
   "source_span_rev": "ff03af16474ce91c89eb3bc28182866f4cb6dfb0",