Avoid C++ unused goto symbol warning when liburing is not supported

[ibc]

When compiling worker in macOS (for example) we got this warnings:

../../../src/handles/TcpConnectionHandle.cpp:270:1: warning: unused label 'write_libuv' [-Wunused-label]
write_libuv:
^~~~~~~~~~~~
1 warning generated.

../../../src/handles/UdpSocketHandle.cpp:195:1: warning: unused label 'send_libuv' [-Wunused-label]
send_libuv:
^~~~~~~~~~~
1 warning generated.

This PR fixes them.

[jmillan]

That's right. Here a cleaner approach:

Simply do not define the tags outside the ifdef.

diff --git a/worker/src/handles/TcpConnectionHandle.cpp b/worker/src/handles/TcpConnectionHandle.cpp
index f254ce867..dd7095ec1 100644
--- a/worker/src/handles/TcpConnectionHandle.cpp
+++ b/worker/src/handles/TcpConnectionHandle.cpp
@@ -265,9 +265,10 @@ void TcpConnectionHandle::Write(

                return;
        }
-#endif

 write_libuv:
+#endif
+
        const size_t totalLen = len1 + len2;
        uv_buf_t buffers[2];
        int written{ 0 };
diff --git a/worker/src/handles/UdpSocketHandle.cpp b/worker/src/handles/UdpSocketHandle.cpp
index e5d9c91fa..a963957c6 100644
--- a/worker/src/handles/UdpSocketHandle.cpp
+++ b/worker/src/handles/UdpSocketHandle.cpp
@@ -190,9 +190,10 @@ void UdpSocketHandle::Send(

                return;
        }
-#endif

 send_libuv:
+#endif
+
        // First try uv_udp_try_send(). In case it can not directly send the datagram
        // then build a uv_req_t and use uv_udp_send().

[ibc]

Done.