package/rtmpdump: drop openssl support

package/rtmpdump: drop openssl support

Rtmpdump does not support openssl 1.1.x, has not seen any changes upstream
since 2015, is only used with the gnutls backend in Debian and Fedora.

There exists a 3rd party patch for openssl 1.1.x support:

https://github.com/JudgeZarbi/RTMPDump-OpenSSL-1.1

But there is an open issue reported about a crash in the handshake code
(which is modified by the patch):

https://github.com/JudgeZarbi/RTMPDump-OpenSSL-1.1/issues/1

And the README for the repo states:

I modified a few of the files in the librtmp directory to conform to the new
getters and setters in OpenSSL 1.1.0.  I don't claim to be a security
expert, and neither have I had any experience with OpenSSL in a programming
sense, so I'm not sure exactly if it's correct, but it compiles and seems to
work for what I use it for.

Which does not sound very reassuring, so instead drop the openssl support.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>