Clean up Paragraph Cxx/iOS code after D27238439

Summary:
In my haste to get out D27238439 (aca0f418ba), parts of it are sloppy. Nothing critical and no known bugs, but we should clean up the commented code, and add back these asserts.

Changelog: [Internal]

Reviewed By: sammy-SC

Differential Revision: D27266288

fbshipit-source-id: f242c26401dfc8851cb1ee0ef8911d19d9c1d9ae

React/Fabric/Mounting/ComponentViews/Text/RCTParagraphComponentView.mm

@@ -107,7 +107,6 @@ using namespace facebook::react;
   }
 
   auto textLayoutManager = _state->getData().layoutManager.lock();
-  //  assert(textLayoutManager && "TextLayoutManager must not be `nullptr`.");
 
   if (!textLayoutManager) {
     return;

ReactCommon/react/renderer/components/text/ParagraphShadowNode.cpp

@@ -102,6 +102,8 @@ void ParagraphShadowNode::updateStateIfNeeded(Content const &content) {
 
   auto &state = getStateData();
 
+  react_native_assert(textLayoutManager_);
+
   if (state.attributedString == content.attributedString) {
     return;
   }