Fix a display bug on artifact gems.

It is the result of an earlier commit that merged down artifact definitions. Resolved by changing the name of the diamond face to 'diamond' over 'gem'.

jewel/gems/gem.arc

@@ -2,8 +2,8 @@ Object gem
 name diamond
 race gold and jewels
 type 60
-face gem.111
-animation gem
+face diamond.111
+animation diamond
 nrof 1
 anim_speed 10
 client_anim_random 1

jewel/gems/gem.face

@@ -1,12 +1,12 @@
-animation gem
-gem.111
-gem.112
+animation diamond
+diamond.111
+diamond.112
 mina
-face gem.111
+face diamond.111
 magicmap green
 visibility 100
 end
-face gem.112
+face diamond.112
 magicmap green
 end
 face diamond_exceptional.111

shop/alchemy_diamond_converter.face

@@ -9,5 +9,5 @@ lava.114
 polymorph.112
 polymorph.113
 polymorph.114
-gem.111
+diamond.111
 mina