build: fix rpm packages build on Fedora 32

Tarantool packages build scenario at rpm/tarantool.spec
installs Python packages for Tarantool testing. In some
latest OS like Fedora 32 old Python packages based on
Python 2 version were deprecated and changed to Python 3.
Currently Tarantool testing based on Python 2 which
packages stored at local backport repository and it
should be used from there calling it as python2-* packages.

Issue:
...
No matching package to install: 'python-yaml >= 3.0.9'
...
Not all dependencies satisfied
Error: Some packages could not be found.

Needed for #4599
Closes #4965

rpm/tarantool.spec

@@ -69,18 +69,21 @@ BuildRequires: libunwind-devel
 %undefine _hardened_build
 %endif
 
-# For tests
-%if (0%{?fedora} >= 22 || 0%{?rhel} == 7)
-BuildRequires: python >= 2.7
-BuildRequires: python-six >= 1.9.0
-BuildRequires: python-gevent >= 1.0
-BuildRequires: python-yaml >= 3.0.9
-%endif
+# Set dependences for tests.
+# Do not install unused Python 3 packages which
+# is default since Fedora 31 and CentOS 8.
 %if (0%{?fedora} >= 31 || 0%{?rhel} >= 8)
 BuildRequires: python2 >= 2.7
 BuildRequires: python2-six >= 1.9.0
 BuildRequires: python2-gevent >= 1.0
 BuildRequires: python2-yaml >= 3.0.9
+%else
+%if (0%{?rhel} != 6)
+BuildRequires: python >= 2.7
+BuildRequires: python-six >= 1.9.0
+BuildRequires: python-gevent >= 1.0
+BuildRequires: python-yaml >= 3.0.9
+%endif
 %endif
 
 Name: tarantool