Bump the cache version to 8

Bump the cache version to avoid unexpected behavior in
older version of fontconfig.

There was no real incompatible features introduced in a cache.
But the older version of fontconfig can't deal with variable fonts
and then it failed. To avoid this breakage, you may want to choose
one of options like:

1) Applying this change to fontconfig in host and remove all the
fontconfig caches and then regenerate them by fc-cache linked with
older one and new one. or simply run applications.
You'll see two versions of caches in the cache directories.

2) Remove variable fonts on system and remove all the fontconfig
caches too. then regenerate caches. You'll still see one version of
caches there but without the entries of variable fonts.

After that, the problem should be gone.

https://bugzilla.redhat.com/show_bug.cgi?id=1981500

fontconfig/fontconfig.h

@@ -67,7 +67,7 @@ typedef int		FcBool;
  * it means multiple copies of the font information.
  */
 
-#define FC_CACHE_VERSION_NUMBER	7
+#define FC_CACHE_VERSION_NUMBER	8
 #define _FC_STRINGIFY_(s)    	#s
 #define _FC_STRINGIFY(s)    	_FC_STRINGIFY_(s)
 #define FC_CACHE_VERSION    	_FC_STRINGIFY(FC_CACHE_VERSION_NUMBER)