Fix lint issues (#4545)

For some reason, two lint violations show up on my computer when running
`yarn lint:eslint`. I have attempted to remove `node_modules`, remove
all `dist` directories, remove `.eslintcache`, run `yarn cache clear`,
etc. to no avail. I think an ultimate fix here may be to upgrade ESLint
packages but that would be a larger change, so as egregious as it is,
this commit skirts around the issue by adding some ignore lines.

packages/accounts-controller/src/AccountsController.ts

@@ -892,6 +892,8 @@ export class AccountsController extends BaseController<
 
     const index = Math.max(
       keyringAccounts.length + 1,
+      // ESLint is confused; this is a number.
+      // eslint-disable-next-line @typescript-eslint/restrict-plus-operands
       lastDefaultIndexUsedForKeyringType + 1,
     );
 

packages/assets-controllers/src/NftDetectionController.test.ts

@@ -1411,6 +1411,8 @@ describe('NftDetectionController', () => {
   it('should not call addNFt when the request to Nft API call throws', async () => {
     const selectedAccount = createMockInternalAccount({ address: '0x3' });
     nock(NFT_API_BASE_URL)
+      // ESLint is confused; this is a string.
+      // eslint-disable-next-line @typescript-eslint/restrict-template-expressions
       .get(`/users/${selectedAccount.address}/tokens`)
       .query({
         continuation: '',