Intermittent test failure in windows/conpty/TestConPTY.py

It looks like this test was added in #192657? CC @charles-zablit @Nerixyz

From https://lab.llvm.org/buildbot/#/builders/141/builds/17706 :

```
******************** TEST 'lldb-api :: windows/conpty/TestConPTY.py' FAILED ********************
Script:
--
C:/Users/tcwg/scoop/apps/python/current/python.exe C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/llvm-project/lldb\test\API\dotest.py -u CXXFLAGS -u CFLAGS --env LLVM_LIBS_DIR=C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/./lib --env LLVM_INCLUDE_DIR=C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/include --env LLVM_TOOLS_DIR=C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/./bin --triple aarch64-pc-windows-msvc --build-dir C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/lldb-test-build.noindex --lldb-module-cache-dir C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/lldb-test-build.noindex/module-cache-lldb\lldb-api --clang-module-cache-dir C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/lldb-test-build.noindex/module-cache-clang\lldb-api --executable C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/./bin/lldb.exe --compiler C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/./bin/clang.exe --dsymutil C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/./bin/dsymutil.exe --make C:/Users/tcwg/scoop/shims/make.exe --llvm-tools-dir C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/./bin --lldb-obj-root C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/tools/lldb --lldb-libs-dir C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/./lib --cmake-build-type Release --skip-category=watchpoint --env LLDB_LAUNCH_FLAG_USE_PIPES=1 C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\lldb\test\API\windows\conpty -p TestConPTY.py
--
Exit Code: 1
Command Output (stdout):
--
lldb version 23.0.0git (https://github.com/llvm/llvm-project.git revision da2c4a9efe996e8a6acf02576be9b39cd69a06df)
clang revision da2c4a9efe996e8a6acf02576be9b39cd69a06df
llvm revision da2c4a9efe996e8a6acf02576be9b39cd69a06df
Skipping the following test categories: watchpoint, libc++, libstdcxx, dwo, dsym, gmodules, debugserver, objc, fork, pexpect
--
Command Output (stderr):
--
PASS: LLDB (C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\build\bin\clang.exe-aarch64) :: test_basic_output_without_vt_check (TestConPTY.ConPTYTestCase.test_basic_output_without_vt_check)
FAIL: LLDB (C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\build\bin\clang.exe-aarch64) :: test_large_output (TestConPTY.ConPTYTestCase.test_large_output)
Log Files:
- C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\build\lldb-test-build.noindex\windows\conpty\TestConPTY\Failure_test_large_output.log
PASS: LLDB (C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\build\bin\clang.exe-aarch64) :: test_stdout_delivery (TestConPTY.ConPTYTestCase.test_stdout_delivery)
PASS: LLDB (C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\build\bin\clang.exe-aarch64) :: test_vt_init_stripped (TestConPTY.ConPTYTestCase.test_vt_init_stripped)
======================================================================
FAIL: test_large_output (TestConPTY.ConPTYTestCase.test_large_output)
ConPTY delivers all output lines when output spans multiple reads.
----------------------------------------------------------------------
Traceback (most recent call last):
File "C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\lldb\test\API\windows\conpty\TestConPTY.py", line 79, in test_large_output
self.assertEqual(
AssertionError: 500 != 499 : Got fewer lines than expected.
Config=aarch64-C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\build\bin\clang.exe
----------------------------------------------------------------------
Ran 4 tests in 6.659s
FAILED (failures=1)
--
********************
```