curl_multi_remove_handle.3: use at any time, just not from within callbacks

[ci skip]

docs/libcurl/curl_multi_remove_handle.3

@@ -5,7 +5,7 @@
 .\" *                            | (__| |_| |  _ <| |___
 .\" *                             \___|\___/|_| \_\_____|
 .\" *
-.\" * Copyright (C) 1998 - 2014, Daniel Stenberg, <daniel@haxx.se>, et al.
+.\" * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
 .\" *
 .\" * This software is licensed as described in the file COPYING, which
 .\" * you should have received as part of this distribution. The terms
@@ -37,6 +37,9 @@ perfectly legal to invoke \fIcurl_easy_perform(3)\fP on this easy handle.
 Removing an easy handle while being used is perfectly legal and will
 effectively halt the transfer in progress involving that easy handle. All
 other easy handles and transfers will remain unaffected.
+
+It is fine to remove a handle at any time during a transfer, just not from
+within any libcurl callback function.
 .SH RETURN VALUE
 CURLMcode type, general libcurl multi interface error code.
 .SH "SEE ALSO"