Bump required git version to 2.39

[jerry-skydio]

This is one older than the latest release, and is required
for new flags as well as the merge-tree command.

Topic: bump
Reviewers: brian-k

[jerry-skydio]

Reviews in this chain:
└#97 Bump required git version to 2.39

[jerry-skydio]

#	head	base	diff	date	summary
0	18dab97a	fa4e5a9a	diff	Apr 4 1:30 AM	1 file changed, 1 insertion(+), 1 deletion(-)
1	d0a212fa	fa4e5a9a	diff	Apr 4 3:02 AM	0 files changed
2	18dab97a	fa4e5a9a	diff	Apr 4 7:31 AM	0 files changed
3	1bf7e142	1a86af93	diff	Apr 4 19:01 PM	0 files changed
4	4671bd4c	1a86af93	diff	Apr 4 19:02 PM	0 files changed