Fix Scala 2.12 eta-expansion for verifyParquetMagic [databricks]

[firestarman]

Fixes #15475.

Description

• Explicitly eta-expand verifyParquetMagic when passing it to PerfIO.readParquetFooterBuffer so Scala 2.12 (DB 14.3 / 350db143) compiles; Scala 2.13 already auto-eta-expands and is unchanged.
• Unblocks Databricks nightly pre-release builds that failed at GpuParquetScan.scala:573 with missing argument list for method verifyParquetMagic.
• Validate: mvn -Dbuildver=330 -Dcuda.version=cuda13 -DskipTests -pl sql-plugin compile and validate on Scala 2.12.

Checklists

Documentation

• Updated for new or modified user-facing features or behaviors
• No user-facing change

Testing

• Added or modified tests to cover new code paths
• Covered by existing tests
  (Please provide the names of the existing tests in the PR description.)
• Not required

Performance

• Tests ran and results are added in the PR description
• Issue filed with a link in the PR description
• Not required

[greptile-apps]

Greptile Summary

This PR fixes Scala 2.12 compilation of the Parquet footer-reading path.

• Explicitly eta-expands verifyParquetMagic when passing it to PerfIO.readParquetFooterBuffer.
• Preserves the existing runtime behavior and Scala 2.13 compatibility.

Confidence Score: 5/5

The PR appears safe to merge because it makes a narrowly scoped Scala 2.12 compatibility fix without changing behavior.

The added underscore converts the existing verifyParquetMagic method reference into the function value expected by readParquetFooterBuffer, while preserving the same callback and arguments.

Important Files Changed

Filename	Overview
sql-plugin/src/main/scala/com/nvidia/spark/rapids/parquet/GpuParquetScan.scala	Explicitly eta-expands an existing method reference to restore Scala 2.12 compilation without changing runtime behavior.

_{Reviews (1): Last reviewed commit: "Fix Scala 2.12 eta-expansion for verifyP..." | Re-trigger Greptile}

[firestarman]

build