Remove tab completion for CREATE UNLOGGED MATERIALIZED VIEW.

Commit 3bf3ab8c56 added support for unlogged materialized views,
but commit 3223b25ff7 reverted that feature before it made it into
a release.  However, the latter commit left the grammar and
tab-completion support intact.  This commit removes the
tab-completion support to prevent psql from recommending bogus
commands.  I've opted to keep the grammar support so that the
server continues to emit a descriptive error when users try to
create unlogged matviews.

Reported-by: Daniel Westermann, px shi
Author: Dagfinn Ilmari Mannsåker
Discussion: https://postgr.es/m/ZR0P278MB092093E92263DE16734208A5D2C59%40ZR0P278MB0920.CHEP278.PROD.OUTLOOK.COM
Discussion: https://postgr.es/m/CAAccyY%2BWg1Z-9tNfSwLmuZVgGOwqU5u1OP-RWcoAr2UZGuvN_w%40mail.gmail.com

src/bin/psql/tab-complete.c

@@ -3267,15 +3267,9 @@ psql_completion(const char *text, int start, int end)
 	/* Complete "CREATE TEMP/TEMPORARY" with the possible temp objects */
 	else if (TailMatches("CREATE", "TEMP|TEMPORARY"))
 		COMPLETE_WITH("SEQUENCE", "TABLE", "VIEW");
-	/* Complete "CREATE UNLOGGED" with TABLE, SEQUENCE or MATVIEW */
+	/* Complete "CREATE UNLOGGED" with TABLE or SEQUENCE */
 	else if (TailMatches("CREATE", "UNLOGGED"))
-	{
-		/* but not MATVIEW in CREATE SCHEMA */
-		if (HeadMatches("CREATE", "SCHEMA"))
-			COMPLETE_WITH("TABLE", "SEQUENCE");
-		else
-			COMPLETE_WITH("TABLE", "SEQUENCE", "MATERIALIZED VIEW");
-	}
+		COMPLETE_WITH("TABLE", "SEQUENCE");
 	/* Complete PARTITION BY with RANGE ( or LIST ( or ... */
 	else if (TailMatches("PARTITION", "BY"))
 		COMPLETE_WITH("RANGE (", "LIST (", "HASH (");