Merge pull request #24 from Nexters/fix/23-update-sr-history-schema

fix: sr before를 not nullable로 변경

Author: eric-jy-park

src/main/java/com/climbup/climbup/sr/entity/SRHistory.java

@@ -35,7 +35,7 @@ public class SRHistory extends BaseEntity {
     @JoinColumn(name = "mission_id", nullable = false)
     private RouteMission mission;
 
-    @Column(name = "sr_before")
+    @Column(name = "sr_before", nullable = false)
     private Integer srBefore;
 
     @Column(name = "sr_after", nullable = false)