Update dependency org.postgresql:postgresql to v42.6.0

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
org.postgresql:postgresql (source)	42.5.4 -> 42.6.0

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Release Notes

pgjdbc/pgjdbc

v42.6.0

Changed

fix: use PhantomReferences instead of Obejct.finalize() to track Connection leaks PR #​2847

The change replaces all uses of Object.finalize with PhantomReferences.
The leaked resources (Connections) are tracked in a helper thread that is active as long as
there are connections in use. By default, the thread keeps running for 30 seconds after all
the connections are released. The timeout is set with pgjdbc.config.cleanup.thread.ttl system property.

refactor:(loom) replace the usages of synchronized with ReentrantLock PR #​2635
Fixes Issue #​1951

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