Remove explicit wrapper versions from build.gradle files

Allows easier updating of the wrappers using:

./gradlew wrapper --gradle-version=X.Y.Z

btypes_big_integer/build.gradle

@@ -51,7 +51,3 @@ tasks.withType(JavaExec) {
 
     systemProperty "java.library.path", "./"
 }
-
-wrapper {
-    gradleVersion = "7.4.2"
-}
\ No newline at end of file

btypes_primitives/build.gradle

@@ -50,7 +50,3 @@ tasks.withType(JavaExec) {
 
     systemProperty "java.library.path", "./"
 }
-
-wrapper {
-    gradleVersion = "7.4.2"
-}
\ No newline at end of file

build.gradle

@@ -69,12 +69,6 @@ task fatJar(type: Jar) {
     with jar
 }
 
-wrapper {
-    gradleVersion = "7.4.2"
-}
-
-
-
 sourceCompatibility = 1.8
 targetCompatibility = 1.8