Remove stray "=back". This was causing newer versions of pod2man to choke.

Reviewed-by: Richard Levitte <levitte@openssl.org>

doc/ssl/SSL_get_extms_support.pod

diff --git a/doc/ssl/SSL_get_extms_support.pod b/doc/ssl/SSL_get_extms_support.pod
index 427819a..4e24824 100644
--- a/doc/ssl/SSL_get_extms_support.pod
+++ b/doc/ssl/SSL_get_extms_support.pod
@@ -24,8 +24,6 @@
 progress i.e. it is not possible to determine if extended master secret
 was used.
 
-=back
-
 =head1 SEE ALSO
 
 L<ssl(3)|ssl(3)>