guix: use git-minimal over git

From the git-minimal package definition:
> The size of the closure of 'git-minimal' is two thirds that of 'git'.
> Its test suite runs slightly faster and most importantly it doesn't
> depend on packages that are expensive to build such as Subversion.

We don't need any fancy / additional git functionality above the basics,
so switch to git-minimal and save some CPU, while also pruning the
greater dependency graph.

```diff
-name: git
+name: git-minimal
 version: 2.37.3
 outputs:
-+ send-email: see Appendix H
-+ svn: see Appendix H
-+ credential-netrc: see Appendix H
-+ credential-libsecret: see Appendix H
-+ subtree: see Appendix H
-+ gui: see Appendix H
 + out: everything else
-systems: x86_64-linux mips64el-linux aarch64-linux powerpc64le-linux i686-linux armhf-linux powerpc-linux
-dependencies: asciidoc@9.1.0 bash-minimal@5.1.8 bash@5.1.8 curl@7.79.1 docbook-xsl@1.79.2 expat@2.4.1 gettext-minimal@0.21 glib@2.70.2 libsecret@0.20.4 openssl@1.1.1l pcre2@10.37 perl-authen-sasl@2.16 perl-cgi@4.52
-+ perl-io-socket-ssl@2.068 perl-net-smtp-ssl@1.04 perl-term-readkey@2.38 perl@5.34.0 pkg-config@0.29.2 python@3.9.9 subversion@1.14.1 tcl@8.6.11 tk@8.6.11.1 xmlto@0.0.28 zlib@1.2.11
-location: gnu/packages/version-control.scm:222:2
+systems: x86_64-linux mips64el-linux aarch64-linux powerpc64le-linux riscv64-linux i686-linux armhf-linux powerpc-linux
+dependencies: bash-minimal@5.1.8 bash@5.1.8 curl@7.79.1 expat@2.4.1 gettext-minimal@0.21 openssl@1.1.1l perl@5.34.0 zlib@1.2.11
+location: gnu/packages/version-control.scm:608:2
 homepage: https://git-scm.com/
 license: GPL 2
 synopsis: Distributed version control system
```

contrib/guix/manifest.scm

@@ -618,7 +618,7 @@ inspecting signatures in Mach-O binaries.")
         perl
         python-3
         ;; Git
-        git
+        git-minimal
         ;; Tests
         (fix-ppc64-nx-default lief))
   (let ((target (getenv "HOST")))