fix(deps): update module github.com/bufbuild/buf to v1.28.1 (master)

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
github.com/bufbuild/buf	require	patch	v1.28.0 -> v1.28.1

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Release Notes

bufbuild/buf (github.com/bufbuild/buf)

v1.28.1

Compare Source

• The buf curl command has been updated to support the use of multiple schemas.
  This allows users to specify multiple --schema flags and/or to use both --schema
  and --reflect flags at the same time. The result is that additional sources can
  be consulted to resolve an element. This can be useful when the result of an RPC
  contains extensions or values in google.protobuf.Any messages that are not defined
  in the same schema that defines the RPC service.
• Fix issue where buf lint incorrectly reports error when (buf.validate.field).required
  is set for an optional field in proto3.

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