[clang-format][NFC] Improve documentation of FixNamespaceComments

[HazardyKnusperkeks]

Summary

Fixes https://github.com/llvm/llvm-project/issues/55162

[owenpan]

clang/include/clang/Format/Format.h

2124–2126

Or something like that?

2132

short is a C++ keyword.

clang/docs/ClangFormatStyleOptions.rst

**ExperimentalAutoDetectBinPacking** (``Boolean``) :versionbadge:`clang-format 3.7`
   made, clang-format analyzes whether there are other bin-packed cases in
   the input file and act accordingly.
 
   NOTE: This is an experimental flag, that might go away or be renamed. Do
   not use this in config files, etc. Use at your own risk.
 
 **FixNamespaceComments** (``Boolean``) :versionbadge:`clang-format 5`
   If ``true``, clang-format adds missing namespace end comments for
-  short namespaces and fixes invalid existing ones. Short ones are
-  controlled by "ShortNamespaceLines".
+  namespaces and fixes invalid existing ones. This doesn't affect short
+  namespaces, which are controlled by ``ShortNamespaceLines``.
 
   .. code-block:: c++
 
      true:                                  false:
-     namespace a {                  vs.     namespace a {
-     foo();                                 foo();
-     bar();                                 bar();
+     namespace longNamespace {      vs.     namespace longNamespace {
+     void foo();                            void foo();
+     void bar();                            void bar();
      } // namespace a                       }
+     namespace shortNamespace {             namespace shortNamespace {
+     void baz();                            void baz();
+     }                                      }
 
 **ForEachMacros** (``List of Strings``) :versionbadge:`clang-format 3.7`
   A vector of macros that should be interpreted as foreach loops
   instead of as function calls.
 
   These are expected to be macros of the form:
 
   .. code-block:: c++

clang/include/clang/Format/Format.h

   /// the input file and act accordingly.
   ///
   /// NOTE: This is an experimental flag, that might go away or be renamed. Do
   /// not use this in config files, etc. Use at your own risk.
   /// \version 3.7
   bool ExperimentalAutoDetectBinPacking;
 
   /// If ``true``, clang-format adds missing namespace end comments for
-  /// short namespaces and fixes invalid existing ones. Short ones are
-  /// controlled by "ShortNamespaceLines".
+  /// namespaces and fixes invalid existing ones. This doesn't affect short
+  /// namespaces, which are controlled by ``ShortNamespaceLines``.
   /// \code
   ///    true:                                  false:
-  ///    namespace a {                  vs.     namespace a {
-  ///    foo();                                 foo();
-  ///    bar();                                 bar();
+  ///    namespace longNamespace {      vs.     namespace longNamespace {
+  ///    void foo();                            void foo();
+  ///    void bar();                            void bar();
   ///    } // namespace a                       }
+  ///    namespace shortNamespace {             namespace shortNamespace {
+  ///    void baz();                            void baz();
+  ///    }                                      }
   /// \endcode
   /// \version 5
   bool FixNamespaceComments;
 
   /// A vector of macros that should be interpreted as foreach loops
   /// instead of as function calls.
   ///
   /// These are expected to be macros of the form: