Replace NOLINT(runtime/explicit) comments with NOLINT (NFC) (#2992)

cpplint.py can accept either, but clang-tidy requires NOLINT.

wpiutil/src/test/native/cpp/sigslot/recursive.cpp

@@ -39,7 +39,7 @@ namespace {
 
 template <typename T>
 struct object {
-  object(T i) : v{i} {}  // NOLINT(runtime/explicit)
+  object(T i) : v{i} {}  // NOLINT
 
   void inc_val(const T& i) {
     if (i != v) {

wpiutil/src/test/native/cpp/sigslot/signal.cpp

@@ -507,7 +507,7 @@ TEST(Signal, SignalMoving) {
 template <typename T>
 struct object {
   object();
-  object(T i) : v{i} {}  // NOLINT(runtime/explicit)
+  object(T i) : v{i} {}  // NOLINT
 
   const T& val() const { return v; }
   T& val() { return v; }