Bug 1392842 - Add intermittency and intermittence to the en-US dictionary. r=ehsan

extensions/spellcheck/locales/en-US/hunspell/en-US.dic

@@ -1,4 +1,4 @@
-52362
+52364
 0/nm
 0th/pt
 1/n1
@@ -31320,6 +31320,8 @@ intermezzo/MS
 interminably
 intermingle/DSG
 intermission/SM
+intermittence/S
+intermittency/S
 intermittent/Y
 intermix/GDS
 internal/SY