[Improvement][Dao] Remove duplicated mysql configurations (#4558)

dolphinscheduler-dao/src/main/resources/datasource.properties

@@ -15,12 +15,6 @@
 # limitations under the License.
 #
 
-# mysql
-#spring.datasource.driver-class-name=com.mysql.jdbc.Driver
-#spring.datasource.url=jdbc:mysql://localhost:3306/dolphinscheduler?useUnicode=true&characterEncoding=UTF-8
-#spring.datasource.username=root
-#spring.datasource.password=123456
-
 # postgresql
 spring.datasource.driver-class-name=org.postgresql.Driver
 spring.datasource.url=jdbc:postgresql://127.0.0.1:5432/dolphinscheduler
@@ -33,7 +27,6 @@ spring.datasource.password=test
 #spring.datasource.username=xxxx
 #spring.datasource.password=xxxx
 
-
 # connection configuration
 #spring.datasource.initialSize=5
 # min connection number