Revert "[clangd] Add a (currently hidden) --strong-workspace-mode flag (#155905)"
This reverts commit 2fa492726e774c050d6f21d57990c8bfbd7f1400.
This caused sanitizer bots to fail and sanitizer errors to show up in
our downstream testing:
```
[ RUN ] LSPTest.DiagnosticsHeaderSaved
<<< initialize: {}
<-- initialize(0)
third_party/llvm/llvm-project/clang-tools-extra/clangd/ClangdLSPServer.cpp:557:14: runtime error: load of value 112, which is not a valid value for type 'bool'
```
With ASan at -O1.