rTorrent: Upgrade to v6.3

## Version 6.3 Release
**This release is recommended for additional stability and performance.**

1. Fixed a possible crash on shutdown caused by improper termination of the curl stack.
2. Improved software performance by using emplace instead of push on `std::array` objects.

## What's Changed
* Replace push with emplace by stickz in stickz/rtorrent#56
* Fixed curl stack shutdown with active downloads by stickz in stickz/rtorrent#57


**Full Changelog**: stickz/rtorrent@v6.2-0.9.8-0.13.8...v6.3-0.9.8-0.13.8

Dockerfile

@@ -12,8 +12,8 @@ ARG RUTORRENT_VERSION=699af5f45fef33d8f2b57792ffe7a48d084f2bed
 ARG GEOIP2_RUTORRENT_VERSION=4ff2bde530bb8eef13af84e4413cedea97eda148
 ARG DUMP_TORRENT_VERSION=302ac444a20442edb4aeabef65b264a85ab88ce9
 
-# v6.2-0.9.8-0.13.8
-ARG RTORRENT_STICKZ_VERSION=0165b4b6dde384d30c2b41ae6d6a2cd23b55c71e
+# v6.3-0.9.8-0.13.8
+ARG RTORRENT_STICKZ_VERSION=ddbbe8a03fb94cf95ab9a6d7fd5c60e51c0353ba
 
 ARG ALPINE_VERSION=3.19
 ARG ALPINE_S6_VERSION=${ALPINE_VERSION}-2.2.0.3