refactor : 커넥션 풀 최대 300으로 설정 (#197)

Author: wjdwnsdnjs13

infrastructure/src/main/resources/application-jpa.yaml

@@ -4,6 +4,8 @@ spring:
         username: ${DB_USERNAME}
         password: ${DB_PASSWORD}
         driver-class-name: com.mysql.cj.jdbc.Driver
+        hikari:
+            maximum-pool-size: 300
 
     jpa:
         database: mysql