update h2 to 2.0.202

Note that this version is NOT backwards compatible with 1.x version

Hence, we use a new DB path "captcha2". The contents in the old DB can be reused
by following instructions in
https://github.com/h2database/h2database/releases/tag/version-2.0.202

src/main/scala/lc/database/DB.scala

@@ -3,7 +3,7 @@ package lc.database
 import java.sql._
 
 class DBConn() {
-  val con: Connection = DriverManager.getConnection("jdbc:h2:./data/H2/captcha", "sa", "")
+  val con: Connection = DriverManager.getConnection("jdbc:h2:./data/H2/captcha2", "sa", "")
 
   def getStatement(): Statement = {
     con.createStatement()