chore(internal-api): Clean up unused method

Author: PerfectSlayer

internal-api/src/main/java/datadog/trace/util/Strings.java

@@ -5,7 +5,6 @@
 import java.nio.charset.StandardCharsets;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
-import java.util.Locale;
 import java.util.concurrent.ThreadLocalRandom;
 import javax.annotation.Nonnull;
 
@@ -142,10 +141,6 @@ public static String trim(final String string) {
     return null == string ? "" : string.trim();
   }
 
-  private static String hex(char ch) {
-    return Integer.toHexString(ch).toUpperCase(Locale.ENGLISH);
-  }
-
   public static String sha256(String input) throws NoSuchAlgorithmException {
     MessageDigest digest = MessageDigest.getInstance("SHA-256");
     byte[] hash = digest.digest(input.getBytes(StandardCharsets.UTF_8));