[SPARK-51194][BUILD] Upgrade scalafmt to 3.8.6

### What changes were proposed in this pull request?

This PR aims to upgrade `scalafmt`  from 3.8.5 to 3.8.6.

### Why are the changes needed?

Update to the latest version, and there are some bug fixes in version 3.8.6:
- RedundantBraces: check comment in scala3 ArgClause
- RedundantBraces: not every Ident continues Infix
- Router: handle braces around context bounds
- Format strings and interpolated strings consistently

Full release notes: https://github.com/scalameta/scalafmt/releases/tag/v3.8.6

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Manually test and Pass GA.

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes #49924 from wayneguow/scalafmt_upgrade.

Authored-by: Wei Guo <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

dev/.scalafmt.conf

@@ -27,4 +27,4 @@ danglingParentheses.preset = false
 docstrings.style = Asterisk
 maxColumn = 98
 runner.dialect = scala213
-version = 3.8.5
+version = 3.8.6