[clangd][NFC] Remove unnecessary vector.

[njames93]

Summary

As pointed out in D92788.

[kbobyrev]

Ah, I see now, thanks for the follow-up!

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

if (!Result) {
     ADD_FAILURE() << "No symbol named " << QName << " in "
                   << ::testing::PrintToString(Slab);
     assert(false && "No symbol with QName");
   }
   return *Result;
 }
 
 const NamedDecl &findDecl(ParsedAST &AST, llvm::StringRef QName) {
-  llvm::SmallVector<llvm::StringRef> Components;
-  QName.split(Components, "::");
-
   auto &Ctx = AST.getASTContext();
   auto LookupDecl = [&Ctx](const DeclContext &Scope,
                            llvm::StringRef Name) -> const NamedDecl & {
     auto LookupRes = Scope.lookup(DeclarationName(&Ctx.Idents.get(Name)));
     assert(!LookupRes.empty() && "Lookup failed");
     assert(LookupRes.size() == 1 && "Lookup returned multiple results");
     return *LookupRes.front();
   };
 
   const DeclContext *Scope = Ctx.getTranslationUnitDecl();
-  for (auto NameIt = Components.begin(), End = Components.end() - 1;
-       NameIt != End; ++NameIt) {
-    Scope = &cast<DeclContext>(LookupDecl(*Scope, *NameIt));
+
+  StringRef Cur, Rest;
+  for (std::tie(Cur, Rest) = QName.split("::"); !Rest.empty();
+       std::tie(Cur, Rest) = Rest.split("::")) {
+    Scope = &cast<DeclContext>(LookupDecl(*Scope, Cur));
   }
-  return LookupDecl(*Scope, Components.back());
+  return LookupDecl(*Scope, Cur);
 }
 
 const NamedDecl &findDecl(ParsedAST &AST,
                           std::function<bool(const NamedDecl &)> Filter) {
   struct Visitor : RecursiveASTVisitor<Visitor> {
     decltype(Filter) F;
     llvm::SmallVector<const NamedDecl *, 1> Decls;
     bool VisitNamedDecl(const NamedDecl *ND) {