Default `#[schemars(deny_unknown_fields)] for json-language-server schemas (#33883)

Followup to #33678, doing the same thing for all JSON Schema files
provided to json-language-server

Release Notes:

* Added warnings for unknown fields when editing `tasks.json` /
`snippets.json`.

crates/task/src/task_template.rs

@@ -4,6 +4,7 @@ use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
 use sha2::{Digest, Sha256};
 use std::path::PathBuf;
+use util::schemars::DefaultDenyUnknownFields;
 use util::serde::default_true;
 use util::{ResultExt, truncate_and_remove_front};
 
@@ -116,6 +117,7 @@ impl TaskTemplates {
     /// Generates JSON schema of Tasks JSON template format.
     pub fn generate_json_schema() -> serde_json_lenient::Value {
         let schema = schemars::generate::SchemaSettings::draft2019_09()
+            .with_transform(DefaultDenyUnknownFields)
             .into_generator()
             .root_schema_for::<Self>();