Fixes for comments in test_bitmapset

This fixes a typo in the sql/expected test files and removes a
leftover comment from test_bitmapset.c from when the functions
invoked bms_free.

Author: Daniel Gustafsson <daniel@yesql.se>
Reported-by: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/978D21E8-9D3B-40EA-A4B1-F87BABE7868C@yesql.se

src/test/modules/test_bitmapset/expected/test_bitmapset.out

@@ -479,7 +479,7 @@ SELECT test_bms_difference('(b 1 3 5)', '(b 1 3 5)') AS result;
  <>
 (1 row)
 
--- Substraction to empty
+-- Subtraction to empty
 SELECT test_bms_difference('(b 42)', '(b 42)') AS result;
  result 
 --------

src/test/modules/test_bitmapset/sql/test_bitmapset.sql

@@ -130,7 +130,7 @@ SELECT test_bms_difference('(b 1 3 5)', '(b 3 5 7)') AS result;
 SELECT test_bms_difference('(b 1 3 5)', '(b 2 4 6)') AS result;
 -- Identical sets
 SELECT test_bms_difference('(b 1 3 5)', '(b 1 3 5)') AS result;
--- Substraction to empty
+-- Subtraction to empty
 SELECT test_bms_difference('(b 42)', '(b 42)') AS result;
 -- Subtraction edge case
 SELECT test_bms_difference(

src/test/modules/test_bitmapset/test_bitmapset.c

@@ -543,8 +543,6 @@ test_bms_join(PG_FUNCTION_ARGS)
 	/* either input can be recycled */
 	result_bms = bms_join(bms1, bms2);
 
-	/* memory cleanup seems more tricky than it's worth here */
-
 	PG_RETURN_BITMAPSET_AS_TEXT(result_bms);
 }