Clean up warnings (#6325)

src/common/hist_util.cc

@@ -163,7 +163,7 @@ void GHistIndexMatrix::Init(DMatrix* p_fmat, int max_bins) {
     } else {
       common::Span<uint32_t> index_data_span = {index.data<uint32_t>(), n_index};
       SetIndexData(index_data_span, batch_threads, batch, rbegin, nbins,
-                   [](auto idx, auto i) { return idx; });
+                   [](auto idx, auto) { return idx; });
     }
 
     #pragma omp parallel for num_threads(nthread) schedule(static)

src/common/version.cc

@@ -16,7 +16,7 @@ namespace xgboost {
 
 const Version::TripletT Version::kInvalid {-1, -1, -1};
 
-Version::TripletT Version::Load(Json const& in, bool check) {
+Version::TripletT Version::Load(Json const& in) {
   if (get<Object const>(in).find("version") == get<Object const>(in).cend()) {
     return kInvalid;
   }

src/common/version.h

@@ -18,7 +18,7 @@ struct Version {
   static const TripletT kInvalid;
 
   // Save/Load version info to Json document
-  static TripletT Load(Json const& in, bool check = false);
+  static TripletT Load(Json const& in);
   static void Save(Json* out);
 
   // Save/Load version info to dmlc::Stream