chore: minor improvement for docs (#4616)

Signed-off-by: bigmoonbit <bigmoonbit@outlook.com>

include/fmt/format.h

@@ -737,7 +737,7 @@ template <typename T>
 using is_double_double = bool_constant<std::numeric_limits<T>::digits == 106>;
 
 // An allocator that uses malloc/free to allow removing dependency on the C++
-// standard libary runtime. std::decay is used for back_inserter to be found by
+// standard library runtime. std::decay is used for back_inserter to be found by
 // ADL when applied to memory_buffer.
 template <typename T> struct allocator : private std::decay<void> {
   using value_type = T;