Everywhere: Remove accidental '\n' from various outln() invocations

Also convert outln(stderr, ...) to warnln(...)

Userland/Applications/Debugger/main.cpp

@@ -83,7 +83,7 @@ static bool handle_backtrace_command(const PtraceRegisters& regs)
 {
     auto ebp_val = regs.ebp;
     auto eip_val = regs.eip;
-    outln("Backtrace:\n");
+    outln("Backtrace:");
     while (g_debug_session->peek((u32*)eip_val).has_value() && g_debug_session->peek((u32*)ebp_val).has_value()) {
         auto eip_symbol = g_debug_session->symbolicate(eip_val);
         auto source_position = g_debug_session->get_source_position(eip_val);

Userland/Libraries/LibCpp/Tests/strace.cpp

@@ -48,7 +48,7 @@ int main(int argc, char** argv)
     int status;
     if (g_pid == -1) {
         if (child_argv.is_empty()) {
-            outln(stderr, "strace: Expected either a pid or some arguments\n");
+            warnln("strace: Expected either a pid or some arguments");
             return 1;
         }
 

Userland/Libraries/LibJS/AST.cpp

@@ -1158,7 +1158,7 @@ void FunctionNode::dump(int indent, const String& class_name) const
     outln("{} '{}'", class_name, name());
     if (!m_parameters.is_empty()) {
         print_indent(indent + 1);
-        outln("(Parameters)\n");
+        outln("(Parameters)");
 
         for (auto& parameter : m_parameters) {
             print_indent(indent + 2);

Userland/Utilities/strace.cpp

@@ -68,7 +68,7 @@ int main(int argc, char** argv)
     int status;
     if (g_pid == -1) {
         if (child_argv.is_empty()) {
-            outln(stderr, "strace: Expected either a pid or some arguments\n");
+            warnln("strace: Expected either a pid or some arguments");
             return 1;
         }