officejs_support_request_ui_test: reduce tolerance and update snapshots

Using verifyImageMatchSnapshot with 20 is sometimes not enough to detect
some significant differences

bt5/erp5_officejs_support_request_ui_test/PathTemplateItem/portal_tests/officejs_support_request_ui_zuite/testFrontPageDashboardLastMonthActivity-reference-snapshot-1.png.xml

@@ -28,7 +28,7 @@
         </item>
         <item>
             <key> <string>width</string> </key>
-            <value> <int>390</int> </value>
+            <value> <int>488</int> </value>
         </item>
       </dictionary>
     </pickle>

bt5/erp5_officejs_support_request_ui_test/PathTemplateItem/portal_tests/officejs_support_request_ui_zuite/testFrontPageDashboardLastMonthActivity.zpt

@@ -64,7 +64,7 @@
 <tr><td colspan="3"><b>Verify the rendering of the graph matches our reference snapshot</b></td></tr>
 <tr><td>verifyImageMatchSnapshot</td>
     <td>//canvas</td>
-    <td>20</td></tr>
+    <td>0</td></tr>
 
 <tr><td colspan="3"><b>Clicking on a serie filter the listbox of recent updates</b></td></tr>
 

bt5/erp5_officejs_support_request_ui_test/PathTemplateItem/portal_tests/officejs_support_request_ui_zuite/testFrontPageDashboardSupportRequestPipe-reference-snapshot-1.png.xml

@@ -28,7 +28,7 @@
         </item>
         <item>
             <key> <string>width</string> </key>
-            <value> <int>404</int> </value>
+            <value> <int>503</int> </value>
         </item>
       </dictionary>
     </pickle>

bt5/erp5_officejs_support_request_ui_test/PathTemplateItem/portal_tests/officejs_support_request_ui_zuite/testFrontPageDashboardSupportRequestPipe.zpt

@@ -81,7 +81,7 @@
 <tr><td colspan="3"><b>Verify the rendering of the graph matches our reference snapshot</b></td></tr>
 <tr><td>verifyImageMatchSnapshot</td>
     <td>//canvas</td>
-    <td>20</td></tr>
+    <td>0</td></tr>
 
 
 <tr><td colspan="3"><b>Clicking on a serie filter the listbox of recent updates</b></td></tr>