Updated gene count used in GeneRandomizedTest to account for the new gene BackReferenceRxGene.

Author: lmasroca

core/src/test/kotlin/org/evomaster/core/search/gene/GeneNumberOfGenesTest.kt

@@ -13,7 +13,7 @@ class GeneNumberOfGenesTest : AbstractGeneTest() {
             This number should not change, unless you explicitly add/remove any gene.
             if so, update this number accordingly
          */
-        assertEquals(88, geneClasses.size)
+        assertEquals(89, geneClasses.size)
     }
 
 }