Respect users' pip.conf

Users may have other pip indices configured in the pip.conf file to pull packages from trusted sources. Please make changes to respect user's pip.conf index-url

[relevant line of code](https://github.com/bridgecrewio/prisma-cloud-vscode-plugin/blob/4b88382839c77850fc034231d1a0df4d30174019/src/commands/checkov/install.ts#L80)