Fix comments in sample config to be correctly marked as verbatim

The comments were not marked as verbatim and thus the Sphinx compiler to generate
the online admin manual interpreted backslashes as special chars. They disappeared
from the output.
By adding ``, it is marked as verbatim and the backslashes are not removed.

Signed-off-by: Christian Wolf <github@christianwolf.email>

config/config.sample.php

@@ -1193,7 +1193,7 @@ $CONFIG = [
 
 /**
  * Set the URL of the Imaginary service to send image previews to.
- * Also requires the OC\Preview\Imaginary provider to be enabled.
+ * Also requires the ``OC\Preview\Imaginary`` provider to be enabled.
  *
  * See https://github.com/h2non/imaginary
  */
@@ -1205,33 +1205,33 @@ $CONFIG = [
  * The following providers are disabled by default due to performance or privacy
  * concerns:
  *
- *  - OC\Preview\Illustrator
- *  - OC\Preview\HEIC
- *  - OC\Preview\Movie
- *  - OC\Preview\MSOffice2003
- *  - OC\Preview\MSOffice2007
- *  - OC\Preview\MSOfficeDoc
- *  - OC\Preview\PDF
- *  - OC\Preview\Photoshop
- *  - OC\Preview\Postscript
- *  - OC\Preview\StarOffice
- *  - OC\Preview\SVG
- *  - OC\Preview\TIFF
- *  - OC\Preview\Font
+ *  - ``OC\Preview\Illustrator``
+ *  - ``OC\Preview\HEIC``
+ *  - ``OC\Preview\Movie``
+ *  - ``OC\Preview\MSOffice2003``
+ *  - ``OC\Preview\MSOffice2007``
+ *  - ``OC\Preview\MSOfficeDoc``
+ *  - ``OC\Preview\PDF``
+ *  - ``OC\Preview\Photoshop``
+ *  - ``OC\Preview\Postscript``
+ *  - ``OC\Preview\StarOffice``
+ *  - ``OC\Preview\SVG``
+ *  - ``OC\Preview\TIFF``
+ *  - ``OC\Preview\Font``
  *
  *
  * Defaults to the following providers:
  *
- *  - OC\Preview\BMP
- *  - OC\Preview\GIF
- *  - OC\Preview\JPEG
- *  - OC\Preview\MarkDown
- *  - OC\Preview\MP3
- *  - OC\Preview\PNG
- *  - OC\Preview\TXT
- *  - OC\Preview\XBitmap
- *  - OC\Preview\OpenDocument
- *  - OC\Preview\Krita
+ *  - ``OC\Preview\BMP``
+ *  - ``OC\Preview\GIF``
+ *  - ``OC\Preview\JPEG``
+ *  - ``OC\Preview\MarkDown``
+ *  - ``OC\Preview\MP3``
+ *  - ``OC\Preview\PNG``
+ *  - ``OC\Preview\TXT``
+ *  - ``OC\Preview\XBitmap``
+ *  - ``OC\Preview\OpenDocument``
+ *  - ``OC\Preview\Krita``
  */
 'enabledPreviewProviders' => [
 	'OC\Preview\PNG',
@@ -2283,8 +2283,8 @@ $CONFIG = [
 /**
  * Allows to override the default scopes for Account data.
  * The list of overridable properties and valid values for scopes are in
- * OCP\Accounts\IAccountManager. Values added here are merged with
- * default values, which are in OC\Accounts\AccountManager
+ * ``OCP\Accounts\IAccountManager``. Values added here are merged with
+ * default values, which are in ``OC\Accounts\AccountManager``.
  *
  * For instance, if the phone property should default to the private scope
  * instead of the local one: