📝 fix docs (#5217)

docs/mkdocs/docs/api/basic_json/number_unsigned_t.md

@@ -32,7 +32,6 @@ With the default values for `NumberUnsignedType` (`std::uint64_t`), the default
 - The restrictions about leading zeros are not enforced in C++. Instead, leading zeros in integer literals lead to an
   interpretation as an octal number. Internally, the value will be stored as a decimal number. For instance, the C++
   integer  literal `010` will be serialized to `8`. During deserialization, leading zeros yield an error.
-- Not-a-number (NaN) values will be serialized to `null`.
 
 #### Limits
 
@@ -45,7 +44,7 @@ when used in a constructor. During deserialization, too large or small integer n
 as [`number_integer_t`](number_integer_t.md) or [`number_float_t`](number_float_t.md).
 
 [RFC 8259](https://tools.ietf.org/html/rfc8259) further states:
-> Note that when such software is used, numbers that are integers and are in the range \f$[-2^{53}+1, 2^{53}-1]\f$ are
+> Note that when such software is used, numbers that are integers and are in the range $[-2^{53}+1, 2^{53}-1]$ are
 > interoperable in the sense that implementations will agree exactly on their numeric values.
 
 As this range is a subrange (when considered in conjunction with the `number_integer_t` type) of the exactly supported