fix(deps): Update A2A SDK to 0.3.0

PiperOrigin-RevId: 789758797

Author: holtskinner

pyproject.toml

@@ -81,7 +81,7 @@ dev = [
 
 a2a = [
   # go/keep-sorted start
-  "a2a-sdk>=0.2.16,<0.3.0;python_version>='3.10'",
+  "a2a-sdk>=0.3.0,<1.0.0;python_version>='3.10'",
   # go/keep-sorted end
 ]