Improve tab completion for ALTER TABLE ALTER COLUMN SET in psql.

The commit changes the tab completion to add DATA TYPE after
ALTER TABLE ... ALTER COLUMN ... SET.

Author: Vignesh C
Reviewed-by: Shubham Khanna, Masahiko Sawada
Discussion: https://postgr.es/m/CALDaNm1aEdJb-QJi%3DGWStkfj_%2BEDUK_VtDkn%2BTjQ2z7HyU0MBw%40mail.gmail.com

Author: MasahikoSawada

src/bin/psql/tab-complete.c

@@ -2507,7 +2507,8 @@ psql_completion(const char *text, int start, int end)
 	/* ALTER TABLE ALTER [COLUMN] <foo> SET */
 	else if (Matches("ALTER", "TABLE", MatchAny, "ALTER", "COLUMN", MatchAny, "SET") ||
 			 Matches("ALTER", "TABLE", MatchAny, "ALTER", MatchAny, "SET"))
-		COMPLETE_WITH("(", "COMPRESSION", "DEFAULT", "EXPRESSION", "GENERATED", "NOT NULL", "STATISTICS", "STORAGE",
+		COMPLETE_WITH("(", "COMPRESSION", "DATA TYPE", "DEFAULT", "EXPRESSION", "GENERATED", "NOT NULL",
+					  "STATISTICS", "STORAGE",
 		/* a subset of ALTER SEQUENCE options */
 					  "INCREMENT", "MINVALUE", "MAXVALUE", "START", "NO", "CACHE", "CYCLE");
 	/* ALTER TABLE ALTER [COLUMN] <foo> SET ( */