fix(stream): Fix table#createReadStream with startIndex

[maximebedard]

Identical PR to #1100, but for table#createReadStream with a startIndex.

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Fixes #1099 🦕

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[loferris]

This looks promising! We're going to need unit tests and integration tests before moving forward. It may be a while before I can write them myself, but if you'd like to take a look, I'd start by adding a unit test around here:

nodejs-bigquery/test/table.ts

Line 1969 in df1dcd3

it('should make correct API request', done => {