[clangd] Fix elog message when preamble build fails.

clang-tools-extra/clangd/Preamble.cpp

vlog("Built preamble of size {0} for file {1} version {2}",
          BuiltPreamble->getSize(), FileName, Inputs.Version);
     std::vector<Diag> Diags = PreambleDiagnostics.take();
     return std::make_shared<PreambleData>(
         Inputs, std::move(*BuiltPreamble), std::move(Diags),
         SerializedDeclsCollector.takeIncludes(),
         SerializedDeclsCollector.takeMacros(), std::move(StatCache),
         SerializedDeclsCollector.takeCanonicalIncludes());
   } else {
-    elog("Could not build a preamble for file {0} version {2}", FileName,
+    elog("Could not build a preamble for file {0} version {1}", FileName,
          Inputs.Version);
     return nullptr;
   }
 }
 
 } // namespace clangd
 } // namespace clang