update Junio's GPG key (with extended expiration)
    
    As explained in 50e6f6e (update Junio's GPG key (with extended
    expiration), 2021-01-27) in the git package¹, the key used to sign git
    releases expired in July 2020.  While this doesn't strictly affect us
    because we use gpgv to verify the releases against a known key file, it
    is worth updating to make it clear that we're using the correct signing
    key.
    
    Here is a diff of the key file before and after the update:
    
        $ diff -u <(gpg gpgkey-96E07AF25771955980DAD10020D04E5A713660A7.asc~ 2>/dev/null) \
                  <(gpg gpgkey-96E07AF25771955980DAD10020D04E5A713660A7.asc 2>/dev/null)
        --- /dev/fd/63	2021-06-05 15:40:47.398256869 -0400
        +++ /dev/fd/62	2021-06-05 15:40:47.399256908 -0400
        @@ -3,6 +3,6 @@
         uid                           Junio C Hamano <gitster@pobox.com>
         uid                           Junio C Hamano <junio@pobox.com>
         uid                           Junio C Hamano <jch@google.com>
        -sub   rsa4096/B0B5E88696AFE6CB 2011-10-03 [S] [expired: 2020-07-26]
        +sub   rsa4096/B0B5E88696AFE6CB 2011-10-03 [S] [expires: 2028-01-11]
         sub   rsa4096/86B76D5D833262C4 2011-10-01 [E]
        -sub   rsa4096/7594EEC7B3F7CAC9 2014-09-20 [S] [expired: 2020-07-26]
        +sub   rsa4096/7594EEC7B3F7CAC9 2014-09-20 [S] [expires: 2028-01-11]
    
    A thread on the git list is where the question was raised and Junio
    confirmed he'd extended the expiration of his signing key².
    
    ¹ https://src.fedoraproject.org/rpms/git/c/50e6f6e
    ² https://lore.kernel.org/git/B6DFB74D-A722-4DBD-A4B2-562604B21CCB@alchemists.io/T/#u