deps: Update dependency asyncpg to v0.28.0

[renovate-bot]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
asyncpg	==0.27.0 -> ==0.28.0

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Release Notes

MagicStack/asyncpg (asyncpg)

v0.28.0

Compare Source

Minor fixes and improvements.

Changes

• Do not try to cleanup statements (#​981)
  (by @​fvannee in d2e710f for #​981)

• Add Pool.is_closing() method (#​973)
  (by @​singingwolfboy in 9cb2c1c for #​973)

• Fix test_tls_version for LibreSSL (#​974)
  (by @​CyberTailor in 7df9812 for #​974)

• Handle environments without home dir (#​1011)
  (by @​LeonardBesson in 172b8f6 for #​1011)

• fix: salt and iterations parsing for scram (#​1026)
  (by @​trigonometr in 7443a9e for #​1026)

• Add support for target_session_attrs (#​987)
  (by @​JesseDeLoore in bf74e88 for #​987)

• Add support for READ UNCOMMITTED (#​1039)
  (by @​benwah in 2f20bae for #​1039)

• Update benchmarks, add psycopg3 (#​1042)
  (by @​elprans in 7d4fcf0 for #​1042)

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