metadata.sql: update PROJ_DATA.VERSION to 1.15

Author: rouault

data/sql/metadata.sql

@@ -18,4 +18,4 @@ INSERT INTO "metadata" VALUES('PROJ.VERSION', '${PROJ_VERSION}');
 
 -- Version of the PROJ-data package with which this database is the most
 -- compatible.
-INSERT INTO "metadata" VALUES('PROJ_DATA.VERSION', '1.14');
+INSERT INTO "metadata" VALUES('PROJ_DATA.VERSION', '1.15');