rpc: Reject beginning newline in RPC docs

It is harmless, but a bit confusing and not needed for new code.

Also, update the remaining instances that were not found by the
scripted-diff.

src/rpc/server.cpp

@@ -156,11 +156,12 @@ static RPCHelpMan help()
 static RPCHelpMan stop()
 {
     static const std::string RESULT{CLIENT_NAME " stopping"};
-    return RPCHelpMan{"stop",
+    return RPCHelpMan{
+        "stop",
     // Also accept the hidden 'wait' integer argument (milliseconds)
     // For instance, 'stop 1000' makes the call wait 1 second before returning
     // to the client (intended for testing)
-                "\nRequest a graceful shutdown of " CLIENT_NAME ".",
+        "Request a graceful shutdown of " CLIENT_NAME ".",
                 {
                     {"wait", RPCArg::Type::NUM, RPCArg::Optional::OMITTED, "how long to wait in ms", RPCArgOptions{.hidden=true}},
                 },