Fix typo on avoid_backing_store_cache param doc (#37985)

Fixes a one character typo spotted in the doc comment for the
avoid_backing_store_cache parameter to the EmbedderExternalViewEmbedder
ctor.
diff --git a/shell/platform/embedder/embedder_external_view_embedder.h b/shell/platform/embedder/embedder_external_view_embedder.h
index 7921cb8..906e5d6 100644
--- a/shell/platform/embedder/embedder_external_view_embedder.h
+++ b/shell/platform/embedder/embedder_external_view_embedder.h
@@ -40,7 +40,7 @@
   /// @brief      Creates an external view embedder used by the generic embedder
   ///             API.
   ///
-  /// @param[in] avoid_backing_store_cache If set, create_render_target callback
+  /// @param[in] avoid_backing_store_cache If set, create_render_target_callback
   ///                                      will beinvoked every frame for every
   ///                                      engine composited layer. The result
   ///                                      will not cached.