build(docs-infra): fix template type check errors (#33066)

In #33066 a limitation of Ivy's template type checker was fixed, where
all directive inputs would incorrectly allow `undefined` to be passed,
even when the input's type did not allow for it. Due to the fix, some
additional type errors were uncovered in AIO, where potential
`undefined` values would be passed to inputs that were not typed to
allow `undefined`.

PR Close #33066

aio/src/app/custom-elements/code/code.component.ts

@@ -63,7 +63,7 @@ export class CodeComponent implements OnChanges {
   @Input() hideCopy: boolean;
 
   /** Language to render the code (e.g. javascript, dart, typescript). */
-  @Input() language: string;
+  @Input() language: string | undefined;
 
   /**
    * Whether to display line numbers:
@@ -71,7 +71,7 @@ export class CodeComponent implements OnChanges {
    *  - If true: show
    *  - If number: show but start at that number
    */
-  @Input() linenums: boolean | number | string;
+  @Input() linenums: boolean | number | string | undefined;
 
   /** Path to the source of the code. */
   @Input() path: string;
@@ -81,12 +81,12 @@ export class CodeComponent implements OnChanges {
 
   /** Optional header to be displayed above the code. */
   @Input()
-  set header(header: string) {
+  set header(header: string | undefined) {
     this._header = header;
     this.ariaLabel = this.header ? `Copy code snippet from ${this.header}` : '';
   }
-  get header(): string { return this._header; }
-  private _header: string;
+  get header(): string|undefined { return this._header; }
+  private _header: string | undefined;
 
   @Output() codeFormatted = new EventEmitter<void>();