fix: change StringContain -> StringReplace (#2095)

subjects/java/piscine/StringReplace/README.md

@@ -23,9 +23,9 @@ Here is a possible ExerciseRunner.java to test your function :
 ```java
 public class ExerciseRunner {
     public static void main(String[] args) {
-        System.out.println(StringContain.replace("javatpoint is a very good website", 'a', 'e'));
+        System.out.println(StringReplace.replace("javatpoint is a very good website", 'a', 'e'));
-        System.out.println(StringContain.replace("my name is khan my name is java", "is","was"));
+        System.out.println(StringReplace.replace("my name is khan my name is java", "is","was"));
-        System.out.println(StringContain.replace("hey i'am java", "I'am","was"));
+        System.out.println(StringReplace.replace("hey i'am java", "I'am","was"));
     }
 }
 ```