simple protocol queries must be run with client_encoding=UTF8

[gongxulei]

Describe the bug
it's not work when pg server param "server_encoding " != utf8.

To Reproduce
Steps to reproduce the behavior:

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Expected behavior
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Actual behavior
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Version

• Go: $ go version -> [e.g. go version go1.18.3 darwin/amd64]
• PostgreSQL: $ psql --no-psqlrc --tuples-only -c 'select version()' -> [e.g. PostgreSQL 14.4 on x86_64-apple-darwin21.5.0, compiled by Apple clang version 13.1.6 (clang-1316.0.21.2.5), 64-bit]
• pgx: $ grep 'github.com/jackc/pgx/v[0-9]' go.mod -> [e.g. v4.16.1]

Additional context
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