typescript compilation issue with proto-loader: 0.6.11

Hi, I'm getting typescript compilation with new version of @grpc/proto-loader: 0.6.11

I have a depencency on 'googleapis'. Previous version resolved was @grpc/proto-loader: 0.6.9 not causing issue. Now it's resolving to 0.6.11 with the following typescript compilation error:

node_modules/@google-cloud/pubsub/build/protos/protos.d.ts:15:23 - error TS2497: This module can only be referenced with ECMAScript imports/exports by turning on the 'esModuleInterop' flag and referencing its default export.

15 import * as Long from "long";
~~~~~~

node_modules/google-gax/build/protos/iam_service.d.ts:17:23 - error TS2497: This module can only be referenced with ECMAScript imports/exports by turning on the 'esModuleInterop' flag and referencing its default export.

17 import * as Long from 'long';
~~~~~~

node_modules/google-gax/build/protos/operations.d.ts:17:23 - error TS2497: This module can only be referenced with ECMAScript imports/exports by turning on the 'esModuleInterop' flag and referencing its default export.

17 import * as Long from 'long';

#### Environment details

- OS: centos8
- Node.js version: 14.16.0
- npm version: 6.14.11
- `googleapis` version: 100.0.0 (same issue in v95)

#### Steps to reproduce

1. npm i
2. npx tsc

Strangely the resolved version on my ubuntu machine is still 0.6.9, but on my centos machine, it resolves to 0.6.11. In the attached repro project, I have explicitely added "@grpc/proto-loader": "0.6.11" to trigger the issue.

Thanks!
[repro.tar.gz](https://github.com/googleapis/google-api-nodejs-client/files/8614617/repro.tar.gz)

Beginne mit dem angehängten Repro-Projekt, führe npm i und npx tsc aus und untersuche, wie @grpc/proto-loader 0.6.11 zusammen mit googleapis und den in den Fehlern genannten generierten .d.ts-Dateien aufgelöst wird. Vergleiche das Ergebnis mit 0.6.9; das Issue ist erledigt, wenn die gemeldeten TypeScript-Kompilierungsfehler unter dem dokumentierten Reproduktions-Setup nicht mehr auftreten.

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