v2.51.0

Changes

• Go 1.16 has GO111Module on by default. This release converts diego-release to be compatible with those changes
• As a result of the conversion to a Go module release, we updated and moved away from having many of our external dependencies in a submodule to a vendored package.

Dependencies

• Bump Golang to go1.16.6 @cf-diego (#578)
• Bump envoy to bf5d0eb44b @cf-diego (#571)