Update jgit version

[staktrace]

The old version of jgit doesn't support DIRC version 4, which
can result in exceptions being thrown by the ratchetFrom
implementation in some situations (likely dependent on the user's
local git version).

See also https://bugs.eclipse.org/bugs/show_bug.cgi?id=565774

[staktrace]

Hi! The PR template says this:

After creating the PR, please add a commit that adds a bullet-point under the `-SNAPSHOT` section of [CHANGES.md](https://github.com/diffplug/spotless/blob/main/CHANGES.md), [plugin-gradle/CHANGES.md](https://github.com/diffplug/spotless/blob/main/plugin-gradle/CHANGES.md), and [plugin-maven/CHANGES.md](https://github.com/diffplug/spotless/blob/main/plugin-maven/CHANGES.md) which includes:

But I don't see a -SNAPSHOT section in CHANGES.md. Is this supposed to refer to the Unreleased section instead?

[nedtwigg]

Is this supposed to refer to the Unreleased section instead?

Yes! Oops, thanks :)

[nedtwigg]

Published in plugin-gradle/6.0.1 and plugin-maven/2.17.5.