Fix README example for Debugf

[aramperes]

Summary

Fixes an example in the README where Debugf is configured to route to fmt.Printf, by using the splat operator to properly unpack format arguments.

Before

• Format arguments not passed properly
• No trailing new-line, hard to read

[send query] compression=["lz4" "((stripped))"] %!s(MISSING)[send data] compression=["lz4"][read data] compression=["lz4" '\x01' '\x00']. block: columns=%!d(MISSING), rows=%!d(MISSING)[read data] compression=["lz4" '\x01' '\x01']. block: columns=%!d(MISSING), rows=%!d(MISSING)[profile info] [rows=1, bytes=256, blocks=1, rows before limit=0, applied limit=false, calculated rows before limit=true][progress] [rows=83256135, bytes=83250374, total rows=83256135, wrote rows=0 wrote bytes=0 elapsed=10.628191ms][progress] [rows=83256135, bytes=83250374, total rows=83256135, wrote rows=0 wrote bytes=0 elapsed=10.628191ms][read data] compression=["lz4" '\x06' '0']. block: columns=%!d(MISSING), rows=%!d(MISSING)[profile events] rows=[48][read data] compression=["lz4" '\x00' '\x00']. block: columns=%!d(MISSING), rows=%!d(MISSING)[progress] [rows=0, bytes=0, total rows=0, wrote rows=0 wrote bytes=0 elapsed=137.047µs][progress] [rows=0, bytes=0, total rows=0, wrote rows=0 wrote bytes=0 elapsed=137.047µs][end of stream]%!(EXTRA []interface {}=[])

After

• Format arguments passed properly
• Trailing new-line, readable

[send query] compression="lz4" ((stripped))
[send data] compression="lz4"
[read data] compression="lz4". block: columns=1, rows=0
[read data] compression="lz4". block: columns=1, rows=1
[profile info] rows=1, bytes=256, blocks=1, rows before limit=0, applied limit=false, calculated rows before limit=true
[progress] rows=83256135, bytes=83250374, total rows=83256135, wrote rows=0 wrote bytes=0 elapsed=10.734099ms
[progress] rows=83256135, bytes=83250374, total rows=83256135, wrote rows=0 wrote bytes=0 elapsed=10.734099ms
[read data] compression="lz4". block: columns=6, rows=48
[profile events] rows=48
[read data] compression="lz4". block: columns=0, rows=0
[progress] rows=0, bytes=0, total rows=0, wrote rows=0 wrote bytes=0 elapsed=154.309µs
[progress] rows=0, bytes=0, total rows=0, wrote rows=0 wrote bytes=0 elapsed=154.309µs
[end of stream]

Checklist

Delete items not relevant to your PR:

• Unit and integration tests covering the common scenarios were added
• A human-readable description of the changes was provided to include in CHANGELOG
• For significant changes, documentation in https://github.com/ClickHouse/clickhouse-docs was updated with further explanations or tutorials