Allow some tests to run without network (#20955)

* thttpclient.nim: respect NIM_TESTAMENT_REMOTE_NETWORKING

* tnetconnect.nim: respect NIM_TESTAMENT_REMOTE_NETWORKING

tests/stdlib/tnetconnect.nim

@@ -5,6 +5,7 @@ discard """
 
 import std/net
 from std/strutils import `%`
+from stdtest/testutils import enableRemoteNetworking
 
 # bug #15215
 proc test() =
@@ -25,4 +26,5 @@ proc test() =
   except TimeoutError, OSError:
     fn("www.google.com")
 
-test()
+when enableRemoteNetworking:
+  test()