makedumpfile: remove explicit-lib-dependency zlib

Fix the following error found by rpmlint,
    makedumpfile.x86_64: E: explicit-lib-dependency zlib
    You must let rpm find the library dependencies by itself. Do not put unneeded
    explicit Requires: tags.

Signed-off-by: Coiby Xu <coxu@redhat.com>
Reviewed-by: Philipp Rudo <prudo@redhat.com>
Reviewed-by: Dave Young <dyoung@redhat.com>

kexec-tools.spec

@@ -71,7 +71,6 @@ License: GPL-2.0-only
 URL: https://github.com/makedumpfile/makedumpfile
 
 Conflicts: kexec-tools < 2.0.28-5
-Requires(pre): zlib
 BuildRequires: make
 BuildRequires: gcc
 BuildRequires: zlib-devel