remove eta-expansion

[xuwei-k]

Pull Request Checklist

• Have you read How to write the perfect pull request?
• Have you read through the contributor guidelines?
• Have you referenced any issues you're fixing using commit message keywords?
• Have you added copyright headers to new files?
• Have you checked that both Scala and Java APIs are updated?
• Have you updated the documentation for both Scala and Java sections?
• Have you added tests for any changed functionality?

Helpful things

Fixes

Purpose

remove _

Background Context

this syntax deprecated since Scala 3.4.x.
Scala 2.13.x support this syntax if -Xsource:3

Welcome to Scala 3.4.1 (17.0.11, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.
                                                                                                                                                                                                                                              
scala> def f(x: Int): Int = x
def f(x: Int): Int
                                                                                                                                                                                                                                              
scala> f _
1 warning found
-- Warning: --------------------------------------------------------------------
1 |f _
  |^^^
  |The syntax `<function> _` is no longer supported;
  |you can simply leave out the trailing ` _`
val res0: Int => Int = Lambda$1431/0x000000040150c000@4cc89246

References

[mkurz]

CI fails