pgstatindex: HASH -> hash

Fix the lone error message in the whole source tree to use capitalized
HASH when referring to hash indexes, making it look like all the other
messages.

Someday it would be good to standardize 'B-Tree', 'B-tree', 'btree', and
random other spellings, too, but that's a larger patch ...

Author: Álvaro Herrera

contrib/pgstattuple/expected/pgstattuple.out

@@ -141,11 +141,11 @@ select * from pgstathashindex('test_hashidx');
 select pgstatginindex('test_pkey');
 ERROR:  relation "test_pkey" is not a GIN index
 select pgstathashindex('test_pkey');
-ERROR:  relation "test_pkey" is not a HASH index
+ERROR:  relation "test_pkey" is not a hash index
 select pgstatindex('test_ginidx');
 ERROR:  relation "test_ginidx" is not a btree index
 select pgstathashindex('test_ginidx');
-ERROR:  relation "test_ginidx" is not a HASH index
+ERROR:  relation "test_ginidx" is not a hash index
 select pgstatindex('test_hashidx');
 ERROR:  relation "test_hashidx" is not a btree index
 select pgstatginindex('test_hashidx');

contrib/pgstattuple/pgstatindex.c

@@ -601,7 +601,7 @@ pgstathashindex(PG_FUNCTION_ARGS)
 	if (!IS_HASH(rel))
 		ereport(ERROR,
 				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-				 errmsg("relation \"%s\" is not a HASH index",
+				 errmsg("relation \"%s\" is not a hash index",
 						RelationGetRelationName(rel))));