chore: Add note about PEM format

Author: HofmeisterAn

docs/modules/qdrant.md

@@ -56,9 +56,14 @@ The Qdrant client is configured to validate the TLS certificate using its thumbp
 === "Configure the Qdrant client"
     ```csharp
     --8<-- "tests/Testcontainers.Qdrant.Tests/QdrantSecureContainerTest.cs:ConfigureQdrantClientCertificate-1"
+
     --8<-- "tests/Testcontainers.Qdrant.Tests/QdrantSecureContainerTest.cs:ConfigureQdrantClientCertificate-2"
     ```
 
+!!! note
+
+    Please ensure that both the certificate and private key are provided in PEM format.
+
 ## A Note To Developers
 
 The module creates a container that listens to requests over **HTTP**. The official Qdrant client uses the gRPC APIs to communicate with Qdrant. **.NET Core** and **.NET** support the above example with no additional configuration. However, **.NET Framework** has limited supported for gRPC over HTTP/2, but it can be enabled by: