Documentation/ABI: sysfs-class-firmware-attributes: Fix Sphinx errors

Fix the following warnings from "make htmldocs":

Documentation/ABI/testing/sysfs-class-firmware-attributes:130:
  ERROR: Unexpected indentation.
  ERROR: Unexpected indentation.
  ERROR: Unexpected indentation.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20220324164737.21765-3-hdegoede@redhat.com

Documentation/ABI/testing/sysfs-class-firmware-attributes

@@ -246,9 +246,7 @@ Description:
 					that is being referenced (e.g hdd0, hdd1 etc)
 					This attribute defaults to device 0.
 
-		certificate:
-		signature:
-		save_signature:
+		certificate, signature, save_signature:
 					These attributes are used for certificate based authentication. This is
 					used in conjunction with a signing server as an alternative to password
 					based authentication.
@@ -257,22 +255,27 @@ Description:
 					The attributes can be displayed to check the stored value.
 
 					Some usage examples:
-					Installing a certificate to enable feature:
-						echo <supervisor password > authentication/Admin/current_password
-						echo <signed certificate> > authentication/Admin/certificate
 
-					Updating the installed certificate:
-						echo <signature> > authentication/Admin/signature
-						echo <signed certificate> > authentication/Admin/certificate
+						Installing a certificate to enable feature::
 
-					Removing the installed certificate:
-						echo <signature> > authentication/Admin/signature
-						echo '' > authentication/Admin/certificate
+							echo "supervisor password" > authentication/Admin/current_password
+							echo "signed certificate" > authentication/Admin/certificate
 
-					Changing a BIOS setting:
-						echo <signature> > authentication/Admin/signature
-						echo <save signature> > authentication/Admin/save_signature
-						echo Enable > attribute/PasswordBeep/current_value
+						Updating the installed certificate::
+
+							echo "signature" > authentication/Admin/signature
+							echo "signed certificate" > authentication/Admin/certificate
+
+						Removing the installed certificate::
+
+							echo "signature" > authentication/Admin/signature
+							echo "" > authentication/Admin/certificate
+
+						Changing a BIOS setting::
+
+							echo "signature" > authentication/Admin/signature
+							echo "save signature" > authentication/Admin/save_signature
+							echo Enable > attribute/PasswordBeep/current_value
 
 					You cannot enable certificate authentication if a supervisor password
 					has not been set.
@@ -288,9 +291,10 @@ Description:
 		certificate_to_password:
 					Write only attribute used to switch from certificate based authentication
 					back to password based.
-					Usage:
-						echo <signature> > authentication/Admin/signature
-						echo <password> > authentication/Admin/certificate_to_password
+					Usage::
+
+						echo "signature" > authentication/Admin/signature
+						echo "password" > authentication/Admin/certificate_to_password
 
 
 What:		/sys/class/firmware-attributes/*/attributes/pending_reboot