[cr136] Fix no-unnecessary-type-assertion lint failures

Chromium change:
https://chromium.googlesource.com/chromium/src/+/1ab923732bf942a3c578e71de35f0eb3f2b0b60c

commit 1ab923732bf942a3c578e71de35f0eb3f2b0b60c
Author: Teresa Mao <temao@chromium.org>
Date:   Wed Mar 5 11:32:50 2025 -0800

    Reland "WebUI: Turn on ESLint rule @typescript-eslint/no-unnecessary-type-assertion."

    This is a reland of commit 7de1bd45a310917a25d59775a7e7eadd33616c3d

    Failures were caused by 1) branded build config which was not included
    in dry run bots and 2) merge conflict.

    Original change's description:
    > WebUI: Turn on ESLint rule @typescript-eslint/no-unnecessary-type-assertion.
    >
    > Fixed: 393525665
    > Change-Id: Ia918404c32a4820e55734be55843fd502acab1b2
    > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6312328
    > Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
    > Commit-Queue: Teresa Mao <temao@chromium.org>
    > Cr-Commit-Position: refs/heads/main@{#1427504}

    Fixed: 393525665

browser/resources/settings/brave_leo_assistant_page/model_list_section.ts

@@ -77,7 +77,7 @@ class ModelListSection extends ModelListSectionBase {
     const isEditing = this.isEditingModelIndex_ !== null
 
     // Since model-config-ui is conditionally rendered, we use this.$$ API to access the element
-    const modelConfigElement = this.$$('#model-config-ui') as any
+    const modelConfigElement: any = this.$$('#model-config-ui')
 
     if (!e.detail.modelConfig.options.customModelOptions) {
       console.error('Custom model options are missing')

browser/resources/settings/brave_overrides/system_page.ts

@@ -36,8 +36,8 @@ RegisterPolymerTemplateModifications({
       // default route, rather than always showing, otherwise when we navigate,
       // we'll get all the toggles showing up.
       const nonStyleChildren = (
-        Array.from(templateContent.children) as HTMLElement[]
-      ).filter((t) => t.tagName !== 'STYLE')
+        Array.from(templateContent.children)
+      ).filter((t: any) => t.tagName !== 'STYLE')
 
       templateContent.appendChild(html`
         <settings-animated-pages id="pages" section="system">