[S06] typo fix: insert missing 'is'

S06-routines.pod

@@ -1099,7 +1099,7 @@ signature, the list is instead evaluated in hyper context, and will
 be asked to split itself into the number of lists corresponding to
 the number of slurpies so declared.  A non-hyperable list will return
 failure for this splitting operation, so the signature should only bind
-on parallelizable list operations.  Likewise a list that "too short to
+on parallelizable list operations.  Likewise a list that is "too short to
 split" fails to bind, so a separate signature may match empty lists,
 and perhaps singletons, if we define "too short" that way.]