Fix mistake in assertFile doc
diff --git a/src/main/java/org/testng/FileAssert.java b/src/main/java/org/testng/FileAssert.java
index f2a4879..f49a3f9 100755
--- a/src/main/java/org/testng/FileAssert.java
+++ b/src/main/java/org/testng/FileAssert.java
@@ -45,7 +45,7 @@
   }
 
   /**
-   * Asserts that a {@code tstvalue} is a proper directory. If it isn't,
+   * Asserts that a {@code tstvalue} is a proper file. If it isn't,
    * an AssertionError, with the given message, is thrown.
    * @param tstvalue the file to evaluate
    * @param message the assertion error message