Fixed wrong filename of logfile in Voxygen's panic message.

Moved the '<date>' component of the logfile name to the
end of the filename string, as RollingFileAppender::new()
appends the date to the provided file name prefix.

Please see
https://docs.rs/tracing-appender/0.1.2/tracing_appender/rolling/struct.RollingFileAppender.html#method.new

voxygen/src/main.rs

@@ -114,7 +114,7 @@ fn main() {
             PanicInfo: {}\n\
             Game version: {} [{}]",
             logs_dir
-                .join("voxygen-<date>.log")
+                .join("voxygen.log.<date>")
                 .display(),
             reason,
             panic_info,