docs(dvls): mark DeletionPolicy supported and fix page title (#6557)

The support matrix left the DeletionPolicy Merge/Delete cell blank for Devolutions
Server, but the provider supports it: GetSecret returns NoSecretErr on a missing
entry (so an ExternalSecret deletionPolicy can detect removal) and DeleteSecret is
implemented. This matches SecretServer, which is already marked in that column.
Also promote the page title from H2 to H1 to match the other provider pages.

Signed-off-by: Alexander Chernov <alexander@chernov.it>
Co-authored-by: Jean-Philippe Evrard <jean-philippe.evrard+rochepub@external.roche.com>

docs/introduction/stability-support.md

@@ -124,7 +124,7 @@ The following table show the support for features across different providers.
 | Chef                             |              |              |                      |                         |        x         |             |                             |
 | Cloud.ru                         |      x       |      x       |                      |            x            |        x         |             |              x              |
 | Delinea                          |              |              |                      |                         |        x         |             |                             |
-| Devolutions Server               |              |              |                      |                         |        x         |      x      |                             |
+| Devolutions Server               |              |              |                      |                         |        x         |      x      |              x              |
 | CyberArk Secrets Manager         |      x       |      x       |                      |            x            |        x         |             |                             |
 | Doppler                          |      x       |              |                      |                         |        x         |             |                             |
 | Fortanix                         |              |              |                      |            x            |        x         |             |                             |

docs/provider/devolutions-server.md

@@ -1,4 +1,4 @@
-## Devolutions Server (DVLS)
+# Devolutions Server (DVLS)
 
 External Secrets Operator integrates with [Devolutions Server](https://devolutions.net/server/) (DVLS) for secret management.