remove disjointness->disjointedness

While `disjointness` is missing from the OED and other mainstream
dictionaries, it is commonly used to descrbe disjoint sets in the
context of mathematics.

codespell_lib/data/dictionary.txt

@@ -22173,7 +22173,6 @@ disired->desired
 disires->desires
 disiring->desiring
 disitributions->distributions
-disjointness->disjointedness
 diskrete->discrete
 diskretion->discretion
 diskretization->discretization