Revert "[clangd] Reapply b60896fa Fall back to selecting...
Revert "[clangd] Reapply b60896fa Fall back to selecting token-before-cursor if token-after-cursor fails."
This reverts commit a2ce807e.
Buildbot failures on GCC due to SelectionTree not being copyable, and
instantiating vector<Selection> in the tweak-handling in ClangdServer.