pyproject.toml: bump packaging minimum version to 20.0.

Signed-off-by: Maxwell G <maxwell@gtmx.me>

Author: gotmax23

pyproject.toml

@@ -210,7 +210,8 @@ cryptography = ">=3.4.7"
 ijson = ">=3.1.4"
 matrix-common = "^1.3.0"
 # We need packaging.requirements.Requirement, added in 16.1.
-packaging = ">=16.1"
+# We need packaging.verison.Version(...).major added in 20.0.
+packaging = ">=20.0"
 # We support pydantic v1 and pydantic v2 via the pydantic.v1 compat module.
 # See https://github.com/matrix-org/synapse/issues/15858
 pydantic = ">=1.7.4, <3"