Updated documentation links for the sentry Monolog integration (#1922)

The old link apparently no longer contains documentation about the
Monolog integration.

sentry/sentry-symfony/3.0/config/packages/prod/sentry.yaml

@@ -6,7 +6,7 @@ sentry:
             - Symfony\Component\Security\Core\Exception\AccessDeniedException
 
 #    If you are using Monolog, you also need this additional configuration to log the errors correctly:
-#    https://docs.sentry.io/platforms/php/guides/symfony/#monolog-integration
+#    https://docs.sentry.io/platforms/php/guides/symfony/integrations/monolog/
 #    register_error_listener: false
 
 # monolog:

sentry/sentry-symfony/4.0/config/packages/sentry.yaml

@@ -3,7 +3,7 @@ when@prod:
         dsn: '%env(SENTRY_DSN)%'
 
 #        If you are using Monolog, you also need this additional configuration to log the errors correctly:
-#        https://docs.sentry.io/platforms/php/guides/symfony/#monolog-integration
+#        https://docs.sentry.io/platforms/php/guides/symfony/integrations/monolog/
 #        register_error_listener: false
 
 #    monolog:

sentry/sentry-symfony/4.6/config/packages/sentry.yaml

@@ -8,7 +8,7 @@ when@prod:
             enabled: false
 
 #        If you are using Monolog, you also need this additional configuration to log the errors correctly:
-#        https://docs.sentry.io/platforms/php/guides/symfony/#monolog-integration
+#        https://docs.sentry.io/platforms/php/guides/symfony/integrations/monolog/
 #        register_error_listener: false
 #        register_error_handler: false
 

sentry/sentry-symfony/5.0/config/packages/sentry.yaml

@@ -10,7 +10,7 @@ when@prod:
                 - 'Symfony\Component\Debug\Exception\FatalErrorException'
 #
 #        # If you are using Monolog, you also need this additional configuration to log the errors correctly:
-#        # https://docs.sentry.io/platforms/php/guides/symfony/#monolog-integration
+#        # https://docs.sentry.io/platforms/php/guides/symfony/integrations/monolog/
 #        register_error_listener: false
 #        register_error_handler: false
 #