update Jason's GPG key (with extended expiration)
    
    The key used to sign the cgit releases had its expiration date extended
    a few months back.  Pull the updated key from Jason Donenfeld's web
    site¹.
    
    Here is a diff of the key file before and after the update:
    
        $ diff -u <(gpg gpgkey-AB9942E6D4A4CFC3412620A749FC7012A5DE03AE.asc~ 2>/dev/null) \
                  <(gpg gpgkey-AB9942E6D4A4CFC3412620A749FC7012A5DE03AE.asc 2>/dev/null)
        --- /dev/fd/63	2021-06-05 15:43:30.494570491 -0400
        +++ /dev/fd/62	2021-06-05 15:43:30.495570529 -0400
        @@ -1,4 +1,4 @@
        -pub   rsa4096/49FC7012A5DE03AE 2011-01-15 [SC] [expired: 2021-02-02]
        +pub   rsa4096/49FC7012A5DE03AE 2011-01-15 [SC] [expires: 2022-02-11]
               AB9942E6D4A4CFC3412620A749FC7012A5DE03AE
         uid                           Jason A. Donenfeld <Jason@zx2c4.com>
        -sub   rsa4096/D4F7A95DFB1EFB7F 2011-01-15 [E] [expired: 2021-02-02]
        +sub   rsa4096/D4F7A95DFB1EFB7F 2011-01-15 [E] [expires: 2022-02-11]
    
    While here, fix a missing space in the comment which includes the URL to
    this key in the spec file.
    
    ¹ https://www.zx2c4.com/keys/AB9942E6D4A4CFC3412620A749FC7012A5DE03AE.asc