BridgeJS: Emit protocol array for-loop as a single CodeBlockItemSyntax

[krodak]

Overview

Fixes the formatter mis-rendering flagged by @kateinoigakukun in swiftwasm#714 so we can land the swift-syntax 603 bump on CI.

The protocol array lowering in StackCodegen.lowerProtocolArrayStatements built its for-loop from three separate CodeBlockItemSyntax fragments ("for ... {", body line, "}"). swift-syntax 603's formatter then rendered the closing brace glued to the previous line, producing output like:

for __bjs_elem_ret in ret {
_swift_js_push_i32((__bjs_elem_ret as! _BridgedSwiftProtocolExportable).bridgeJSLowerAsProtocolReturn())}

This change combines the for-loop into a single multi-line CodeBlockItemSyntax using a string-interpolated multi-line literal, matching the pattern already used for nullable protocol return lowering a bit further up in the file. The formatter now produces consistent output across swift-syntax 600/601/602/603:

for __bjs_elem_ret in ret {
    _swift_js_push_i32((__bjs_elem_ret as! _BridgedSwiftProtocolExportable).bridgeJSLowerAsProtocolReturn())
}

The only affected snapshot is Protocol.swift (two occurrences).

Verification

Ran the BridgeJS test suite against every swift-syntax version the CI matrix covers, all 105/106 tests passing:

• `swift test --package-path ./Plugins/BridgeJS` (default 600.0.1)
• `BRIDGEJS_OVERRIDE_SWIFT_SYNTAX_VERSION=601.0.0 swift test ...`
• `BRIDGEJS_OVERRIDE_SWIFT_SYNTAX_VERSION=602.0.0 swift test ...`
• `BRIDGEJS_OVERRIDE_SWIFT_SYNTAX_VERSION=603.0.0 swift test ...`

Merge this into `chore/relax-swift-syntax-constraint` and the PR's CI matrix should go green.

[krodak]

Superseded by swiftwasm#716, which covers this fix and more (all three StackCodegen for-loop helpers + the struct/enum consumer trivia-glue bug). The protocol-array lowering fix from this PR is already merged into swiftwasm/JavaScriptKit as part of swiftwasm#716.