Revert "db: increase db module level in vlib "

This reverts commit cd6d175180.

examples/database/mysql.v

@@ -1,4 +1,4 @@
-// import db.mysql
+// import mysql
 
 // pub fn main() {
 // 	conn := mysql.connect('localhost', 'root', '', 'mysql')
@@ -11,5 +11,5 @@
 // }
 
 fn main() {
-
-}
+	
+}