irc: change default value of server option "tls_priorities" to NORMAL

It is no more needed to remove `VERS-SSL3.0` because it is no longer in the
default priorities since GnuTLS 3.4.0 (released on 2015-04-08).

ChangeLog.adoc

@@ -18,6 +18,7 @@ New features::
   * core: display only version with command `/version`, add options `-o` and `-ol` in command `/upgrade`
   * core: add number of processes in command `/sys waitpid`
   * core, alias, trigger: allow wildcard in commands `/bar`, `/item`, `/proxy`, `/alias` and `/trigger` (issue #1956)
+  * irc: change default value of server option "tls_priorities" to `NORMAL`
   * irc: add support of RGB colors in messages, add option irc.color.term_remap (issue #2025)
   * irc: add tags "nick_xxx" and "host_xxx" in all messages, including self and server messages
   * irc: add option irc.look.ignore_tag_messages (issue #989)

src/plugins/irc/irc-server.c

@@ -86,7 +86,7 @@ char *irc_server_options[IRC_SERVER_NUM_OPTIONS][2] =
   { "tls",                  "on"                      },
   { "tls_cert",             ""                        },
   { "tls_password",         ""                        },
-  { "tls_priorities",       "NORMAL:-VERS-SSL3.0"     },
+  { "tls_priorities",       "NORMAL"                  },
   { "tls_dhkey_size",       "2048"                    },
   { "tls_fingerprint",      ""                        },
   { "tls_verify",           "on"                      },