Update dependency renovate to ^21.15.1

This MR contains the following updates:

Package	Type	Update	Change
renovate (source)	dependencies	minor	^21.14.0 -> ^21.15.1

MR created with the help of gitlab-org/frontend/renovate-gitlab-bot

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Release Notes

renovatebot/renovate

v21.15.1

Compare Source

21.15.1 (2020-06-22)

Bug Fixes

• clojure: set registryStrategy (4610e25)

v21.15.0

Compare Source

Features

• sbt: Support private variable version resolving (#​6565) (aa9a004)

Code Refactoring

• ExternalHostError (#​6563) (52a074e)

Tests

• move e2e tests (#​6567) (02e6817)

v21.14.1

Compare Source

21.14.1 (2020-06-22)

Bug Fixes

• filter registryUrls for null/undefined (cb84fa9)

Miscellaneous Chores

• deps: update dependency eslint-plugin-import to v2.21.2 (#​6505) (3ba1c93)

Code Refactoring

• simplify global init (#​6452) (f77b7e8)

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