pytest: Move to pygit2 1.6.1

In order to move to a newer distribution for CI, we need to update
pygit2.  Given that bullseye ships with libgit2-1.1.x we can move up to
1.6.1 for pygit2 as it is the newest release that also still uses
libgit2-1.1.x

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/test/py/requirements.txt b/test/py/requirements.txt
index 33c5c0b..3274949 100644
--- a/test/py/requirements.txt
+++ b/test/py/requirements.txt
@@ -12,7 +12,7 @@
 py==1.10.0
 pycryptodomex==3.9.8
 pyelftools==0.27
-pygit2==0.28.2
+pygit2==1.6.1
 pyparsing==2.4.2
 pytest==5.2.1
 python-mimeparse==1.6.0