[lld/COFF] Remove needless indirection

`symtab.ctx.symtab` is just `symtab`. Looks like llvm#119296 added
this using a global find-and-replace.

This was the only instance of `symtab.ctx.symtab` in lld/.

No behavior change.

lld/COFF/SymbolTable.cpp

@@ -116,7 +116,7 @@ static void forceLazy(Symbol *s) {
   }
   case Symbol::Kind::LazyObjectKind: {
     InputFile *file = cast<LazyObject>(s)->file;
-    file->symtab.ctx.symtab.addFile(file);
+    file->symtab.addFile(file);
     break;
   }
   case Symbol::Kind::LazyDLLSymbolKind: {