[libc++][NFC] Fix the the in comment in __format/buffer.h

I made this commit primarily to test my commit access to the LLVM repo

Differential Revision: https://reviews.llvm.org/D131365

Author: vogelsgesang

libcxx/include/__format/buffer.h

@@ -302,7 +302,7 @@ struct _LIBCPP_TEMPLATE_VIS __format_to_n_buffer_base {
 ///
 /// This version is used when \c __enable_direct_output<_OutIt, _CharT> == true.
 ///
-/// This class limits the size available the the direct writer so it will not
+/// This class limits the size available to the direct writer so it will not
 /// exceed the maximum number of code units.
 template <class _OutIt, __formatter::__char_type _CharT>
   requires(output_iterator<_OutIt, const _CharT&>)