Update documentation for barman recover options

Fixes two errors in the documentation for `barman recover` by:

1. Updating the `--gcp-zone` to reflect that it is an option which
   overrides the configured `gcp_zone` rather than a required
   parameter.
2. Adding the `--azure-resource-group` option which was omitted when
   the option was added to the code.

doc/barman.1

@@ -632,10 +632,18 @@ This option is required when recovering backups made with
 .RE
 .TP
 .B \-\-gcp\-zone \f[I]ZONE_NAME\f[]
-Name of the availability zone where the instance and disks for snapshot
+Name of the GCP zone where the instance and disks for snapshot recovery
 are located.
-This option is required when recovering backups made with
-\f[C]backup_method\ =\ snapshot\f[].
+This option can be used to override the value of \f[C]gcp_zone\f[] in
+the Barman config.
+.RS
+.RE
+.TP
+.B \-\-azure\-resource\-group \f[I]RESOURCE_GROUP_NAME\f[]
+Name of the Azure resource group containing the instance and disks for
+snapshot recovery.
+This option can be used to override the value of
+\f[C]azure_resource_group\f[] in the Barman config.
 .RS
 .RE
 .RE

doc/barman.1.d/50-recover.md

@@ -123,6 +123,11 @@ recover *\[OPTIONS\]* *SERVER_NAME* *BACKUP_ID* *DESTINATION_DIRECTORY*
         `backup_method = snapshot`.
 
     --gcp-zone *ZONE_NAME*
-    :   Name of the availability zone where the instance and disks for snapshot
-        are located. This option is required when recovering backups made with
-        `backup_method = snapshot`.
+    :   Name of the GCP zone where the instance and disks for snapshot recovery
+        are located. This option can be used to override the value of `gcp_zone`
+        in the Barman config.
+
+    --azure-resource-group *RESOURCE_GROUP_NAME*
+    :   Name of the Azure resource group containing the instance and disks for
+        snapshot recovery. This option can be used to override the value of
+        `azure_resource_group` in the Barman config.