[clangd] Fix MSVC implicit capture build failure.

MSVC builds were failing because the constexpr wasn't couldn't be captured by the lamdba.

Fix an implicit double to float truncation warning as well.

Author: RKSimon

clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp

@@ -196,10 +196,10 @@ TEST(DecisionForestRankingModel, ReferencesAffectRanking) {
 
 TEST(DecisionForestRankingModel, DecisionForestScorerCallbackTest) {
   clangd::CodeCompleteOptions Opts;
-  constexpr float MagicNumber = 1234.5678;
+  constexpr float MagicNumber = 1234.5678f;
   Opts.RankingModel = CodeCompleteOptions::DecisionForest;
-  Opts.DecisionForestScorer = [](const SymbolQualitySignals &,
-                                 const SymbolRelevanceSignals &, float Base) {
+  Opts.DecisionForestScorer = [&](const SymbolQualitySignals &,
+                                  const SymbolRelevanceSignals &, float Base) {
     DecisionForestScores Scores;
     Scores.Total = MagicNumber;
     Scores.ExcludingName = MagicNumber;