fix grammar in comment in dictobject.c (python#125822)

Author: xylocone

Objects/dictobject.c

@@ -34,7 +34,7 @@ As of Python 3.6, this is compact and ordered. Basic idea is described here:
 
 dk_indices is actual hashtable.  It holds index in entries, or DKIX_EMPTY(-1)
 or DKIX_DUMMY(-2).
-Size of indices is dk_size.  Type of each index in indices is vary on dk_size:
+Size of indices is dk_size.  Type of each index in indices varies with dk_size:
 
 * int8  for          dk_size <= 128
 * int16 for 256   <= dk_size <= 2**15