[client-channel] log formatting cleanup (#38133)

avoid these two variables being printed without intervening whitespace

Closes #38133

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/38133 from ctiller:flake-fightas-24 68090c1251
PiperOrigin-RevId: 697007434

src/core/client_channel/client_channel.cc

@@ -260,7 +260,7 @@ class ClientChannel::SubchannelWrapper::WatcherWrapper
         << subchannel_wrapper_.get() << " subchannel "
         << subchannel_wrapper_->subchannel_.get()
         << " watcher=" << watcher_.get()
-        << "state=" << ConnectivityStateName(state) << " status=" << status;
+        << " state=" << ConnectivityStateName(state) << " status=" << status;
     absl::optional<absl::Cord> keepalive_throttling =
         status.GetPayload(kKeepaliveThrottlingKey);
     if (keepalive_throttling.has_value()) {