Adjust libplacebo dependency for EPEL 9

EPEL 9 now has libplacebo (4.x) and libplacebo6 packages, both -devel
packages provide the same pkgconfig (and therefore conflict) but the
runtimes are parallel-installable.

vlc.spec

@@ -137,7 +137,7 @@ BuildRequires:	pkgconfig(libmtp) >= 1.0.0
 BuildRequires:	pkgconfig(libnfs) >= 1.10.0
 BuildRequires:	pkgconfig(libnotify) pkgconfig(gtk+-3.0)
 %if %{with placebo}
-BuildRequires:	pkgconfig(libplacebo) >= 0.2.1
+BuildRequires:	pkgconfig(libplacebo) < 6
 %endif
 BuildRequires:	pkgconfig(libpostproc)
 %if %{with projectm}