thunderbird: Update version from 52.2.0 to 52.2.1

[Release notes][1]:

> Version 52.2.1, first offered to Release channel users on June 23,
> 2017

> ### What’s New ###
>
> *   Fixed: Problems with Gmail (folders not showing, repeated email
>     download, etc.) introduced in version 52.2.0.
>
> ### Known Issues ###
>
> *   Unresolved: On Windows, "Send to > Mail recipient" does not work.
>     Workaround: Install the Microsoft Visual Studio 2015 redistributable
>     runtime library or the Universal C Runtime for Windows Server.

> *   Unresolved: Multiple requests for master password when GMail OAuth2
>     is enabled

[1]: https://www.mozilla.org/en-US/thunderbird/52.2.1/releasenotes/

thunderbird.be0

@@ -2,7 +2,7 @@
 
 #export BEE_TMP_TMPDIR=/dev/shm BEE_TMP_BUILDROOT=/dev/shm/bee-root BEE_MAKEFLAGS='-j80'
 
-# BEE_VERSION thunderbird-52.2.0-0
+# BEE_VERSION thunderbird-52.2.1-0
 
 SRCURL[0]="https://ftp.mozilla.org/pub/thunderbird/releases/${PKGVERSION}/source/thunderbird-${PKGVERSION}.source.tar.xz"