[api] Remove unused reserve from APIServer constructor (#14017)

esphome/components/api/api_server.cpp

@@ -28,11 +28,7 @@ static const char *const TAG = "api";
 // APIServer
 APIServer *global_api_server = nullptr;  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
 
-APIServer::APIServer() {
-  global_api_server = this;
-  // Pre-allocate shared write buffer
-  shared_write_buffer_.reserve(64);
-}
+APIServer::APIServer() { global_api_server = this; }
 
 void APIServer::setup() {
   ControllerRegistry::register_controller(this);