fix: removed contradictive @NotNull preventing to add data to database.

MyINPulse-back/src/main/java/enseirb/myinpulse/model/SectionCell.java

@@ -1,7 +1,6 @@
 package enseirb.myinpulse.model;
 
 import jakarta.persistence.*;
-import jakarta.validation.constraints.NotNull;
 
 import java.time.LocalDateTime;
 import java.util.ArrayList;
@@ -18,7 +17,6 @@ public class SectionCell {
     private final List<Annotation> listAnnotation = new ArrayList<>();
 
     @Id
-    @NotNull
     @GeneratedValue(strategy = GenerationType.IDENTITY)
     private Long idSectionCell;