[clang] [clang][NFC] Use range-based for loop and algorithms in `SemaDeclCXX.cpp` (PR #169938)

[Timm Baeder via cfe-commits]

================
@@ -13476,23 +13458,22 @@ bool Sema::CheckUsingDeclRedeclaration(SourceLocation UsingLoc,
   }
 
   NestedNameSpecifier CNNS = Qual.getCanonical();
-  for (LookupResult::iterator I = Prev.begin(), E = Prev.end(); I != E; ++I) {
-    NamedDecl *D = *I;
-
+  for (const NamedDecl *D : Prev) {
     bool DTypename;
     NestedNameSpecifier DQual = std::nullopt;
-    if (UsingDecl *UD = dyn_cast<UsingDecl>(D)) {
+    if (const UsingDecl *UD = dyn_cast<UsingDecl>(D)) {
----------------
tbaederr wrote:

```suggestion
    if (const auto *UD = dyn_cast<UsingDecl>(D)) {
```

https://github.com/llvm/llvm-project/pull/169938