test: remove obsolete debugger pre-break handling

[inoway46]

isPreBreak was a compatibility branch for the old node-inspect-era CommonJS wrapper display.

In the current default CommonJS loading path, lib/internal/modules/cjs/loader.js uses compileFunctionForCJSLoader to compile the original file source directly, so the initial break is shown at the user code line, e.g. > 1 const x = 10;.

node/lib/internal/modules/cjs/loader.js

Line 1879 in ed33ae7

const result = compileFunctionForCJSLoader(content, filename, false /* is_sea_main */, shouldDetectModule);

As a result, the branch that detects 1 (function (exports and sends next is not reached by the normal debugger tests and has become unnecessary legacy compatibility code.

This also removes the old optional wrapper pattern from the test-debugger-break.js expectation.

Background

While investigating flakes around waitForInitialBreak(), this branch stood out as unused in the current default path so this PR removes it.