remove head-box dif, because it is unnecessary

pdb-js/src/app/components/datepicker/date-picker.component.html

@@ -1,9 +1,4 @@
 <style>
-  .header-box {
-    display: flex;
-    justify-content: end;
-  }
-
   .date-picker-overlay {
     width: 500px;
     transition: box-shadow 200ms cubic-bezier(0, 0, 0.2, 1);
@@ -27,18 +22,16 @@
   }
 </style>
 
-<div class="header-box">
-  <button
-    mat-button
-    matTooltip="Date Picker"
-    (click)="isOpen = !isOpen"
-    cdkOverlayOrigin
-    #trigger="cdkOverlayOrigin"
-    [attr.disabled]="isDisabled ? 'disabled' : null"
-  >
-    {{ datePickerControl.value?.display }}
-  </button>
-</div>
+<button
+  mat-button
+  matTooltip="Date Picker"
+  (click)="isOpen = !isOpen"
+  cdkOverlayOrigin
+  #trigger="cdkOverlayOrigin"
+  [attr.disabled]="isDisabled ? 'disabled' : null"
+>
+  {{ datePickerControl.value?.display }}
+</button>
 
 <ng-template
   cdkConnectedOverlay