Remove s390x reverse-dependencies on gatb-core

[Sergio Durigan Junior]

gatb-core only compiles for the following architectures:

- amd64
- arm64
- ppc64el
- riscv64

This is done on purpose by Debian, but unfortunately there wasn't a followup to remove the reverse-dependencies from architectures that aren't being built anymore.

On s390x, the revdeps are:

$ reverse-depends -r lunar src:gatb-core -a s390x
Reverse-Recommends
* med-bio (for gatb-core)
* med-bio-dev (for libgatbcore-dev)

Reverse-Depends
* bcalm (for libgatbcore3)
* discosnp (for libgatbcore3)
* discosnp (for gatb-core)
* mindthegap (for libgatbcore3)
* minia (for libgatbcore3)
* simka (for libgatbcore3)

These are all suffering from the same problem: their "Architecture" field needs to be updated in order to reflect the fact that libgatbcore3 isn't available everywhere anymore. Debian is also suffering from the same problem, so I filed a bunch of bugs there and uploaded fixes for all of the packages above.

med-bio and med-bio-dev are "Architecture: all" and shouldn't be a problem.

To reiterate, the following packages are affected in Ubuntu and need to have their list of supported architectures adjusted by ubuntu-archive:

- bcalm
- discosnp
- mindthegap
- minia
- simka
- gatb-core

[Steve Langasek (vorlon)]

Removing packages from lunar:
 bcalm 2.2.3-3 in lunar s390x
Comment: ANAIS
1 package successfully removed.

[Steve Langasek (vorlon)]

Removing packages from lunar:
 discosnp 1:2.6.2-1 in lunar s390x
Comment: ANAIS
1 package successfully removed.

[Steve Langasek (vorlon)]

Removing packages from lunar:
 mindthegap 2.3.0-1 in lunar s390x
Comment: ANAIS
1 package successfully removed.

[Steve Langasek (vorlon)]

Removing packages from lunar:
 minia 3.2.6-2 in lunar s390x
Comment: ANAIS
1 package successfully removed.

[Steve Langasek (vorlon)]

Removing packages from lunar:
 simka 1.5.3-6 in lunar s390x
Comment: ANAIS
1 package successfully removed.

[Steve Langasek (vorlon)]

Removing packages from lunar:
 libgatbcore3 1.4.2+dfsg-10 in lunar s390x
 libgatbcore-dev 1.4.2+dfsg-10 in lunar s390x
 gatb-core 1.4.2+dfsg-10 in lunar s390x
Comment: ANAIS
3 packages successfully removed.