[lldb][test] XcodeSDKModuleTests: remove non-deterministic source mapping checks

This assertion was added to check that `RegisterXcodeSDK` will correctly update the source mappings of the module. However, the source mapping will only get updated if the command-line invocation of `xcrun` succeeded. Even if `xcrun` failed to find an SDK, the source mappings would get an entry (see https://github.com/llvm/llvm-project/blob/f6212c1cd3d8b827c7d7e2f6cf54b135c27eacc6/lldb/source/Host/macosx/objcxx/HostInfoMacOSX.mm#L424-L444). But if the shell invocation itself failed, then the mappings are not updated. This means depending on how slow `xcrun` is on a given host, this test may fail. On my machine this happens consistently in debug and release builds.

This patch removes this flakey assertion. We unfortunately lost some
test coverage here but I'm not sure there's great alternatives unless we
either:
1. Mock the `xcrun` call somehow (we could maybe pass a callable around
   which defaults to `xcrun` in non-test code?)
2. Make a `xcrun` time-out not an error either?

Author: Michael137

lldb/unittests/SymbolFile/DWARF/XcodeSDKModuleTests.cpp

@@ -116,11 +116,8 @@ TEST_F(XcodeSDKModuleTests, TestModuleGetXcodeSDK) {
   SymbolFileDWARF &sym_file = dwarf_cu->GetSymbolFileDWARF();
   CompUnitSP comp_unit = sym_file.GetCompileUnitAtIndex(0);
   ASSERT_TRUE(static_cast<bool>(comp_unit.get()));
-  ModuleSP module = t.GetModule();
-  ASSERT_EQ(module->GetSourceMappingList().GetSize(), 0u);
   XcodeSDK sdk = sym_file.ParseXcodeSDK(*comp_unit);
   ASSERT_EQ(sdk.GetType(), XcodeSDK::Type::MacOSX);
-  ASSERT_EQ(module->GetSourceMappingList().GetSize(), 1u);
 }
 
 TEST_F(XcodeSDKModuleTests, TestSDKPathFromDebugInfo_InvalidSDKPath) {