[libc++][doc] Fixes FeatureTestMacroTable.html.

`utils/generate_feature_test_macro_components.py` uses the wrong
indentation. `:name: feature-status-table :widths: auto` is rendered as
text instead of being used by Sphinx to render the table properly.

This fixes the identation in the souce and updates the generated output.

Reviewed By: #libc, ldionne

Differential Revision: https://reviews.llvm.org/D112251

Author: mordante

libcxx/docs/FeatureTestMacroTable.rst

@@ -18,8 +18,8 @@ Status
 ======
 
 .. table:: Current Status
-     :name: feature-status-table
-     :widths: auto
+    :name: feature-status-table
+    :widths: auto
 
     ================================================= =================
     Macro Name                                        Value

libcxx/utils/generate_feature_test_macro_components.py

@@ -1095,8 +1095,8 @@ def produce_docs():
 ======
 
 .. table:: Current Status
-     :name: feature-status-table
-     :widths: auto
+    :name: feature-status-table
+    :widths: auto
 
 {status_tables}