Revert "Dexpreopt soong modules inside soong"

This reverts commit 29ff88741e.

Test: none
Bug: 119412419

java/config/makevars.go

@@ -65,7 +65,6 @@ func makeVarsProvider(ctx android.MakeVarsContext) {
 	ctx.Strict("JMOD", "${JmodCmd}")
 
 	ctx.Strict("SOONG_JAVAC_WRAPPER", "${SoongJavacWrapper}")
-	ctx.Strict("DEXPREOPT_GEN", "${DexpreoptGen}")
 	ctx.Strict("ZIPSYNC", "${ZipSyncCmd}")
 
 	ctx.Strict("JACOCO_CLI_JAR", "${JacocoCLIJar}")