Tweak MOX reactor description

locale/en/base.cfg

@@ -7,7 +7,7 @@ MOX-reactor=MOX reactor
 breeder-reactor=Breeder reactor
 
 [entity-description]
-MOX-reactor=Less active MOX fuel allows the reactor to have a smaller size than regular.
+MOX-reactor=Less active MOX fuel allows the reactor to have a smaller size than regular and increased efficiency boost when using multiple reactors.
 breeder-reactor=Reactor used for nuclear breeding. Although the direct energy output is low, recycling the used cells yields useful isotopes.
 
 [item-name]