[SIEM] Fix timeline styles in Firefox (elastic#37575)

Fix SIEM timeline styles in Firefox

x-pack/plugins/siem/public/components/flyout/index.tsx

@@ -22,7 +22,7 @@ import { DEFAULT_TIMELINE_WIDTH } from '../timeline/body/helpers';
 import { trackUiAction as track } from '../../lib/track_usage';
 
 /** The height in pixels of the flyout header, exported for use in height calculations */
-export const flyoutHeaderHeight: number = 48;
+export const flyoutHeaderHeight: number = 60;
 
 export const Badge = styled(EuiBadge)`
   position: absolute;

x-pack/plugins/siem/public/components/timeline/properties/styles.tsx

@@ -23,6 +23,10 @@ export const TimelineProperties = styled.div<{ width: number }>`
 
 export const DatePicker = styled(EuiFlexItem)<{ width: number }>`
   width: ${({ width }) => `${width}px`};
+  .euiSuperDatePicker__flexWrapper {
+    max-width: none;
+    width: auto;
+  }
 `;
 
 export const NameField = styled(EuiFieldText)`