Fix type-checking errors in snippets (code only, no .md)

This commit both:
- Fixes pre-existing mistakes in snippets, aka wrong code samples.
- Adds hidden (`@hide`) statements that do not appear in the docs,
  but satisfy typecheckers.

qdrant-landing/content/documentation/headless/snippets/clear-payload/simple/go.go

@@ -7,6 +7,14 @@ import (
 )
 
 func Main() {
+	// @hide-start
+	client, err := qdrant.NewClient(&qdrant.Config{
+	    Host: "localhost",
+	    Port: 6334,
+	})
+	if err != nil { panic(err) }
+	// @hide-end
+
 	client.ClearPayload(context.Background(), &qdrant.ClearPayloadPoints{
 	    CollectionName: "{collection_name}",
 	    Points: qdrant.NewPointsSelector(

qdrant-landing/content/documentation/headless/snippets/clear-payload/simple/java.java

@@ -6,6 +6,11 @@ import java.util.List;
 
 public class Snippet {
         public static void run() throws Exception {
+                // @hide-start
+                io.qdrant.client.QdrantClient client =
+                    new io.qdrant.client.QdrantClient(io.qdrant.client.QdrantGrpcClient.newBuilder("localhost", 6334, false).build());
+                // @hide-end
+
                 client
                     .clearPayloadAsync("{collection_name}", List.of(id(0), id(3), id(100)), true, null, null)
                     .get();

qdrant-landing/content/documentation/headless/snippets/clear-payload/simple/rust.rs

@@ -1,6 +1,8 @@
 use qdrant_client::qdrant::{ClearPayloadPointsBuilder, PointsIdsList};
 
 pub async fn main() -> anyhow::Result<()> {
+    let client = qdrant_client::Qdrant::from_url("http://localhost:6334").build()?; // @hide
+
     client
         .clear_payload(
             ClearPayloadPointsBuilder::new("{collection_name}")