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/insert-points/with-payload/csharp.cs

@@ -30,10 +30,7 @@ public class Snippet
 		            Payload =
 		            {
 		                ["city"] = new[] { "Berlin", "Moscow" },
-		                ["price"] = new Value
-		                {
-		                    ListValue = new ListValue { Values = { new Value[] { 1.99, 2.99 } } }
-		                }
+		                ["price"] = new Value[] { 1.99, 2.99 }
 		            }
 		        }
 		    }

qdrant-landing/content/documentation/headless/snippets/insert-points/with-payload/go.go

@@ -12,6 +12,8 @@ func Main() {
 	    Port: 6334,
 	})
 
+	if err != nil { panic(err) } // @hide
+
 	client.Upsert(context.Background(), &qdrant.UpsertPoints{
 	    CollectionName: "{collection_name}",
 	    Points: []*qdrant.PointStruct{

qdrant-landing/content/documentation/headless/snippets/insert-points/with-payload/java.java

@@ -1,6 +1,7 @@
 package com.example.snippets_amalgamation;
 
 import static io.qdrant.client.PointIdFactory.id;
+import static io.qdrant.client.ValueFactory.list;
 import static io.qdrant.client.ValueFactory.value;
 import static io.qdrant.client.VectorsFactory.vectors;
 

qdrant-landing/content/documentation/headless/snippets/insert-points/with-payload/rust.rs

@@ -1,5 +1,5 @@
 use qdrant_client::qdrant::{PointStruct, UpsertPointsBuilder};
-use qdrant_client::{Payload, Qdrant, QdrantError};
+use qdrant_client::{Payload, Qdrant};
 use serde_json::json;
 
 pub async fn main() -> anyhow::Result<()> {