Set per-stream window delta limit to 1MB (#27298)

diff --git a/src/core/ext/transport/chttp2/transport/flow_control.h b/src/core/ext/transport/chttp2/transport/flow_control.h
index 10fad26..8f266e4 100644
--- a/src/core/ext/transport/chttp2/transport/flow_control.h
+++ b/src/core/ext/transport/chttp2/transport/flow_control.h
@@ -50,7 +50,7 @@
 static constexpr const uint32_t kMinInitialWindowSize = 128;
 static constexpr const uint32_t kMaxInitialWindowSize = (1u << 30);
 // The maximum per-stream flow control window delta to advertise.
-static constexpr const uint32_t kMaxWindowDelta = (1u << 10);
+static constexpr const uint32_t kMaxWindowDelta = (1u << 20);
 
 class TransportFlowControl;
 class StreamFlowControl;