devtool: upgrade: do not add dummy git notes

devtool: upgrade: do not add dummy git notes

This has been causing a significant performance regression,
to the point where AUH wasn't able to complete upgrades with
particularly large number of git commits between releases [1].

After discussing with Peter [2], running 'oe-selftest -r devtool' with this change (100% pass),
and also doing an AUH run with it, and reviewing the output I think this is fine to remove:
the case is either very niche or non-existent, and if it appears again, we
should come up with a better fix.

[1] https://autobuilder.yoctoproject.org/valkyrie/#/builders/38/builds/54/steps/15/logs/stdio
[2] https://lists.openembedded.org/g/openembedded-core/message/231281

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>