Document that Assertions class is not part of the API

JAVA-4795

Author: jyemin

driver-core/src/main/com/mongodb/assertions/Assertions.java

@@ -30,6 +30,8 @@
  * for not using the {@code assert} statements is that they are not always enabled. We prefer having internal checks always done at the
  * cost of our code doing a relatively small amount of additional work in production.
  * The {@code assert...} methods return values to open possibilities of being used fluently.
+ *
+ * <p>This class is not part of the public API and may be removed or changed at any time</p>
  */
 public final class Assertions {
     /**

gradle/javadoc.gradle

@@ -44,6 +44,7 @@ subprojects { project ->
     tasks.withType(Javadoc) {
         dependsOn tagletsProject.compileJava //We need taglets to be compiled
         exclude "**/com/mongodb/**/benchmark/**"
+        exclude "**/com/mongodb/**/assertions/**"
         exclude "**/com/mongodb/**/internal/**"
         exclude "**/org/bson/**/internal/**"
         options {