[clang-tidy] use isConvertingConstructor to simplify code

[thyecust]

Summary

isConvertingConstructor() is a better API.

https://google.github.io/styleguide/cppguide.html#Implicit_Conversions:

constructors that are callable with a single argument, must be marked explicit in the class definition.

[thyecust]

this change looks meaningless now

clang-tools-extra/clang-tidy/google/ExplicitConstructorCheck.cpp

if (Loc.isMacroID())
       return;
     diag(Loc, WarningMessage)
         << Conversion << FixItHint::CreateInsertion(Loc, "explicit ");
     return;
   }
 
   const auto *Ctor = Result.Nodes.getNodeAs<CXXConstructorDecl>("ctor");
   if (Ctor->isOutOfLine() || Ctor->getNumParams() == 0 ||
-      Ctor->getMinRequiredArguments() > 1)
+      Ctor->isConvertingConstructor(true))
     return;
 
   bool TakesInitializerList = isStdInitializerList(
       Ctor->getParamDecl(0)->getType().getNonReferenceType());
   if (Ctor->isExplicit() &&
       (Ctor->isCopyOrMoveConstructor() || TakesInitializerList)) {
     auto IsKwExplicit = [](const Token &Tok) {
       return Tok.is(tok::raw_identifier) &&