chore(liquibase-maven-plugin): update a password to match the one from Docker container.

Fixes login issue when MySQL is running locally with docker compose and prod.yml:

[ERROR] Failed to execute goal org.liquibase:liquibase-maven-plugin:3.5.5:updateSQL (default-cli) on
project mystamps: Error setting up or running Liquibase: liquibase.exception.DatabaseException:
java.sql.SQLException: Access denied for user 'mystamps'@'172.18.0.1' (using password: YES)

[skip ci]

Author: php-coder

src/main/resources/liquibase/liquibase.properties

@@ -1,4 +1,4 @@
 driver = com.mysql.jdbc.Driver
 url = jdbc:mysql://localhost:3306/mystamps?characterEncoding=UTF-8&useSSL=false
 username = mystamps
-password = mystamps
+password = secret