WIP: Stop recommending imagemagick in the admin pages

This tempts admins into installing insecure packages to make the
warning go away, even going so far as to [impurely modify running
containers](nextcloud/docker#1414 (comment)).

Changing the warning to trigger if the php-imagick module is loaded is
more in line with the actual upstream recommendation, and hopefully
helps unsuspecting users who have hacked around the warning in the
past realize this.

Draft because:

- [ ] Untested (will try building this all this evening)
- [ ] Translations are missing

Band-aid for nextcloud#1414, while we wait for a proper solution with libvips
or somesuch.

apps/settings/lib/Controller/CheckSetupController.php

@@ -815,8 +815,8 @@ protected function isEnoughTempSpaceAvailableIfS3PrimaryStorageIsUsed(): bool {
 		return false;
 	}
 
-	protected function imageMagickLacksSVGSupport(): bool {
-		return extension_loaded('imagick') && count(\Imagick::queryFormats('SVG')) === 0;
+	protected function imageMagickLoaded(): bool {
+		return extension_loaded('imagick');
 	}
 
 	/**

core/js/setupchecks.js

@@ -424,13 +424,13 @@
 							type: OC.SetupChecks.MESSAGE_TYPE_INFO
 						})
 					}
-					if (data.imageMagickLacksSVGSupport) {
+					if (data.imageMagickLoaded) {
 						messages.push({
 							msg: t(
 								'core',
-								'Module php-imagick in this instance has no SVG support. For better compatibility it is recommended to install it.'
-							),
-							type: OC.SetupChecks.MESSAGE_TYPE_INFO
+								'Imagemagick is in use for document preview. This is not recommended out of security concerns, see the document preview documentation here:'
+							) + " <a href='https://docs.nextcloud.com/server/stable/admin_manual/configuration_files/previews_configuration.html'>https://docs.nextcloud.com/server/stable/admin_manual/configuration_files/previews_configuration.html</a>",
+							type: OC.SetupChecks.MESSAGE_TYPE_WARNING
 						})
 					}
 					if (data.pendingBigIntConversionColumns.length > 0) {