Removed a typo (#66)

Signed-off-by: Ryan Kennelly <43864586+RyanKennelly03@users.noreply.github.com>
Co-authored-by: Stanislav (Stanley) Modrak <44023416+smith558@users.noreply.github.com>

Author: RyanKennelly03

markdown/source_md/making-our-own-types-and-typeclasses.md

@@ -1083,7 +1083,6 @@ ghci> a .++ b
 ```
 
 Nice.
-Is nice.
 If we wanted, we could implement all of the functions that operate on lists on our own list type.
 
 Notice how we pattern matched on `(x :-: xs)`.