remove crontab guru link (apache#12467)

superset-frontend/src/views/CRUD/alert/components/AlertReportCronScheduler.tsx

@@ -17,19 +17,13 @@
  * under the License.
  */
 import React, { useState, useCallback, useRef, FunctionComponent } from 'react';
-import { styled, t, useTheme } from '@superset-ui/core';
+import { t, useTheme } from '@superset-ui/core';
 
 import { Input, AntdInput } from 'src/common/components';
 import { Radio } from 'src/common/components/Radio';
 import { CronPicker, CronError } from 'src/common/components/CronPicker';
 import { StyledInputContainer } from '../AlertReportModal';
 
-const HelperText = styled.div`
-  display: block;
-  color: ${({ theme }) => theme.colors.grayscale.base};
-  font-size: ${({ theme }) => theme.typography.sizes.s - 1}px;
-  text-align: left;
-`;
 interface AlertReportCronSchedulerProps {
   value: string;
   onChange: (change: string) => any;
@@ -92,17 +86,6 @@ export const AlertReportCronScheduler: FunctionComponent<AlertReportCronSchedule
             </div>
           </StyledInputContainer>
         </div>
-        <HelperText>
-          {t('Refer to the ')}
-          <a
-            href="https://crontab.guru/"
-            target="_blank"
-            rel="noopener noreferrer"
-          >
-            {t('crontab guru')}
-          </a>
-          {t(' for more information on how to structure your CRON schedule.')}
-        </HelperText>
       </Radio.Group>
     </>
   );