Update zulip hash to pick up version that can be analyzed cleanly. (#453)

Removal of macros from dart sdk results in regressing to older versions
of drift, analysis errors.

Example of broken dart flutter hh build:
https://ci.chromium.org/ui/b/8718098337026152721

Author: aam

registry/zulip.test

@@ -2,7 +2,7 @@ contact=greg@zulip.com
 contact=cbobbe@zulip.com
 
 fetch=git clone https://github.com/zulip/zulip-flutter.git tests
-fetch=git -C tests checkout e0dff1e7aa94049b96048c2204d26debe3dc6785
+fetch=git -C tests checkout d302584e53b332d6b503b4d0a9761d4b5c419069
 
 setup.linux=tools/customer-testing/setup.sh