fix(docs): incorrect returns for MutMap.get (#5640)

The `MutMap.get` method throws an error and does not return undefined.

libs/wingc/src/lsp/snapshots/completions/incomplete_if_statement.snap

@@ -34,7 +34,7 @@ source: libs/wingc/src/lsp/completions.rs
   detail: "(key: str): T1"
   documentation:
     kind: markdown
-    value: "```wing\nget: (key: str): T1\n```\n---\nReturns a specified element from the map.\n### Parameters\n- `key` — `str` — The key of the element to return.\n\n### Returns\nThe element associated with the specified key, or undefined if the key can't be found\n\n### Remarks\nIf the value that is associated to the provided key is an object, then you will get a reference\nto that object and any change made to that object will effectively modify it inside the map."
+    value: "```wing\nget: (key: str): T1\n```\n---\nReturns a specified element from the map.\n### Parameters\n- `key` — `str` — The key of the element to return.\n\n### Returns\nThe element associated with the specified key, or throw an error if the key can't be found\n\n### Remarks\nIf the value that is associated to the provided key is an object, then you will get a reference\nto that object and any change made to that object will effectively modify it inside the map."
   sortText: ff|get
   insertText: get($1)
   insertTextFormat: 2

libs/wingsdk/src/std/map.ts

@@ -178,7 +178,7 @@ export class MutMap {
    * @macro ((obj, key) => { if (!(key in obj)) throw new Error(`MutMap does not contain key: "${key}"`); return obj[key]; })($self$, $args$)
    *
    * @param key The key of the element to return.
-   * @returns The element associated with the specified key, or undefined if the key can't be found
+   * @returns The element associated with the specified key, or throw an error if the key can't be found
    */
   public get(key: string): T1 {
     key;