[clangd] Fix argument type (bool->float).

[adamcz]

Summary

The default value is 1.3f, but it was cast to true, which is not a good
base for code completion score.

clang-tools-extra/clangd/tool/ClangdMain.cpp

opt<CodeCompleteOptions::CodeCompletionRankingModel> RankingModel{
     values(clEnumValN(CodeCompleteOptions::Heuristics, "heuristics",
                       "Use hueristics to rank code completion items"),
            clEnumValN(CodeCompleteOptions::DecisionForest, "decision_forest",
                       "Use Decision Forest model to rank completion items")),
     init(CodeCompleteOptions().RankingModel),
     Hidden,
 };
 
-opt<bool> DecisionForestBase{
+opt<float> DecisionForestBase{
     "decision-forest-base",
     cat(Features),
     desc("Base for exponentiating the prediction from DecisionForest."),
     init(CodeCompleteOptions().DecisionForestBase),
     Hidden,
 };
 
 // FIXME: also support "plain" style where signatures are always omitted.