fix(deps): update dependency @google-cloud/bigquery to v6

[renovate-bot]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
@google-cloud/bigquery	^5.5.0 -> ^6.0.0

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Release Notes

googleapis/nodejs-bigquery

### [`v6.0.0`](https://togithub.com/googleapis/nodejs-bigquery/blob/HEAD/CHANGELOG.md#​600-httpsgithubcomgoogleapisnodejs-bigquerycomparev5120v600-2022-05-20) [Compare Source](https://togithub.com/googleapis/nodejs-bigquery/compare/v5.12.0...v6.0.0) ##### ⚠ BREAKING CHANGES - update library to use Node 12 ([#​1114](https://togithub.com/googleapis/nodejs-bigquery/issues/1114)) ##### Features - add custom retry options ([#​1088](https://togithub.com/googleapis/nodejs-bigquery/issues/1088)) ([b7f29ed](https://togithub.com/googleapis/nodejs-bigquery/commit/b7f29ed4f748c8bd0b062bb68cf9de4b2925cace)) ##### Bug Fixes - **deps:** update dependency [@​google-cloud/promisify](https://togithub.com/google-cloud/promisify) to v3 ([#​1112](https://togithub.com/googleapis/nodejs-bigquery/issues/1112)) ([cb0d601](https://togithub.com/googleapis/nodejs-bigquery/commit/cb0d601fa4f8693ffbf4f3eb3f40d2fa014dd8f5)) - Fix Job#getQueryResultsStream when using startIndex ([#​1100](https://togithub.com/googleapis/nodejs-bigquery/issues/1100)) ([2b7df52](https://togithub.com/googleapis/nodejs-bigquery/commit/2b7df52ff6bce5422d5d3724bd635606d584c2dc)) ##### Build System - update library to use Node 12 ([#​1114](https://togithub.com/googleapis/nodejs-bigquery/issues/1114)) ([b49fc4d](https://togithub.com/googleapis/nodejs-bigquery/commit/b49fc4d7a0f623da40f2d40e1d7e223ab23f1965))

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