Revert "[JENKINS-72690] Make the widget sticky (jenkinsci#287)"

When other panels have been added to the side bar, they are shown
overlapping with the stick timestamper panel which has a transparent
background.  That is noticeable with the Collapsible Section plugin
which can generate a fairly long panel.

I understand the use case for making it sticky, but the overlapping text
is concerning.

This reverts commit b2e06b5.

src/main/resources/hudson/plugins/timestamper/annotator/TimestampAnnotatorFactory3/usersettings.jelly

@@ -29,10 +29,6 @@ THE SOFTWARE.
 
   <l:ajax>
     <style>
-      #timestamper-pane {
-        position: sticky;
-        top: 44px;
-      }
       #timestamper-pane .pane-header-title {
         display: flex;
         justify-content: space-between;