devel/cgit: Fix fetch

yasu@rolling-vm-freebsd2[1018]% pwd
/usr/ports/devel/cgit
yasu@rolling-vm-freebsd2[1019]% make fetch

> License GPLv2 accepted by the user

> cgit-1.2.3 depends on file: /usr/local/sbin/pkg - found

> cgit-1.2.3.tar.xz doesn't seem to exist in /net/freebsd/ports/distfiles/.

> Attempting to fetch http://git.zx2c4.com/cgit/snapshot/cgit-1.2.3.tar.xz

fetch: http://git.zx2c4.com/cgit/snapshot/cgit-1.2.3.tar.xz: size unknown
fetch: http://git.zx2c4.com/cgit/snapshot/cgit-1.2.3.tar.xz: size of remote file is not known
cgit-1.2.3.tar.xz 88 kB 353 kBps 00s

> git-2.25.1.tar.xz doesn't seem to exist in /net/freebsd/ports/distfiles/.

> /!\ Error /!\

The :git group used for git-2.25.1.tar.xz is missing
from MASTER_SITES. Check for typos, or errors.

• Error code 1

Stop.
make: stopped in /usr/ports/devel/cgit
yasu@rolling-vm-freebsd2[1020]%

Approved by: portmgr blanket (just fix it)
MFH: 2023Q2

(cherry picked from commit 762f0c8d53d9faa2bd25cfc633220c7be752a536)