Change COLLATION keyword category

It was changed from unreserved to reserved as part of the COLLATION
FOR syntax, but it turns out that type_func_name_keyword is
sufficient.

src/backend/parser/gram.y

@@ -12528,6 +12528,7 @@ col_name_keyword:
 type_func_name_keyword:
 			  AUTHORIZATION
 			| BINARY
+			| COLLATION
 			| CONCURRENTLY
 			| CROSS
 			| CURRENT_SCHEMA
@@ -12571,7 +12572,6 @@ reserved_keyword:
 			| CAST
 			| CHECK
 			| COLLATE
-			| COLLATION
 			| COLUMN
 			| CONSTRAINT
 			| CREATE

src/include/parser/kwlist.h

@@ -79,7 +79,7 @@ PG_KEYWORD("close", CLOSE, UNRESERVED_KEYWORD)
 PG_KEYWORD("cluster", CLUSTER, UNRESERVED_KEYWORD)
 PG_KEYWORD("coalesce", COALESCE, COL_NAME_KEYWORD)
 PG_KEYWORD("collate", COLLATE, RESERVED_KEYWORD)
-PG_KEYWORD("collation", COLLATION, RESERVED_KEYWORD)
+PG_KEYWORD("collation", COLLATION, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("column", COLUMN, RESERVED_KEYWORD)
 PG_KEYWORD("comment", COMMENT, UNRESERVED_KEYWORD)
 PG_KEYWORD("comments", COMMENTS, UNRESERVED_KEYWORD)