Inconsistent comments between 2 templates of unchecked(). (#4519)

This comment is unrelated to having T in tparam or not.
Probably a typo.
Copied the correct one here.

Resolve #4518

include/pybind11/numpy.h

@@ -1121,10 +1121,10 @@ class array_t : public array {
 
     /**
      * Returns a proxy object that provides const access to the array's data without bounds or
-     * dimensionality checking.  Unlike `unchecked()`, this does not require that the underlying
-     * array have the `writable` flag.  Use with care: the array must not be destroyed or reshaped
-     * for the duration of the returned object, and the caller must take care not to access invalid
-     * dimensions or dimension indices.
+     * dimensionality checking.  Unlike `mutable_unchecked()`, this does not require that the
+     * underlying array have the `writable` flag.  Use with care: the array must not be destroyed
+     * or reshaped for the duration of the returned object, and the caller must take care not to
+     * access invalid dimensions or dimension indices.
      */
     template <ssize_t Dims = -1>
     detail::unchecked_reference<T, Dims> unchecked() const & {