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/create-payload-index/integer-is-principal/go.go

@@ -12,6 +12,8 @@ func Main() {
 		Port: 6334,
 	})
 
+	if err != nil { panic(err) } // @hide
+
 	client.CreateFieldIndex(context.Background(), &qdrant.CreateFieldIndexCollection{
 		CollectionName: "{collection_name}",
 		FieldName:      "name_of_the_field_to_index",

qdrant-landing/content/documentation/headless/snippets/create-payload-index/integer-is-principal/java.java

@@ -3,6 +3,7 @@ package com.example.snippets_amalgamation;
 import io.qdrant.client.QdrantClient;
 import io.qdrant.client.QdrantGrpcClient;
 import io.qdrant.client.grpc.Collections.IntegerIndexParams;
+import io.qdrant.client.grpc.Collections.KeywordIndexParams;
 import io.qdrant.client.grpc.Collections.PayloadIndexParams;
 import io.qdrant.client.grpc.Collections.PayloadSchemaType;
 
@@ -18,8 +19,8 @@ public class Snippet {
                         PayloadSchemaType.Integer,
                         PayloadIndexParams.newBuilder()
                             .setIntegerIndexParams(
-                                KeywordIndexParams.newBuilder()
-                                    .setIsPrincipa(true)
+                                IntegerIndexParams.newBuilder()
+                                    .setIsPrincipal(true)
                                     .build())
                             .build(),
                         null,

qdrant-landing/content/documentation/headless/snippets/create-payload-index/integer-is-principal/rust.rs

@@ -3,7 +3,7 @@ use qdrant_client::qdrant::{
     IntegerIndexParamsBuilder,
     FieldType
 };
-use qdrant_client::{Qdrant, QdrantError};
+use qdrant_client::Qdrant;
 
 pub async fn main() -> anyhow::Result<()> {
     let client = Qdrant::from_url("http://localhost:6334").build()?;
@@ -18,7 +18,7 @@ pub async fn main() -> anyhow::Result<()> {
             IntegerIndexParamsBuilder::default()
                 .is_principal(true),
         ),
-    );
+    ).await?;
 
     Ok(())
 }