checkstyle: removed redundant new line

Author: alxkm

src/test/java/com/thealgorithms/strings/PermuteStringTest.java

@@ -5,7 +5,6 @@
 import java.util.HashSet;
 import java.util.Set;
 import java.util.stream.Stream;
-
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.MethodSource;