proxy: don't fully parse the json input for sql-over-http

[conradludgate]

turns out we don't need to fully parse the json input for sql-over-http.

[github-actions]

5184 tests run: 4977 passed, 0 failed, 207 skipped (full report)

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Flaky tests (2)

Postgres 17

• test_isolation[4]: release-x86-64

Postgres 14

• test_lr_with_slow_safekeeper: release-arm64

Code coverage* (full report)

• functions: 31.5% (7570 of 24031 functions)
• lines: 49.2% (60500 of 122869 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
fe8b93a at 2024-10-14T14:23:56.415Z :recycle:}