[lldb][test] XcodeSDKModuleTests: remove non-deterministic source mapping checks (#129526)

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 `Host::RunShellCommand` call to `xcrun`
succeeded. Even if `xcrun` failed to find an SDK, the source mappings
would get an entry. But if the shell invocation itself failed, then the
mappings are not updated (see
https://github.com/llvm/llvm-project/blob/f6212c1cd3d8b827c7d7e2f6cf54b135c27eacc6/lldb/source/Host/macosx/objcxx/HostInfoMacOSX.mm#L424-L444).
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) {