Changed version number to 1.3.15

Changed for library
diff --git a/doxygen/input/doc_mainpage.h b/doxygen/input/doc_mainpage.h
index 2fb694c..3583939 100644
--- a/doxygen/input/doc_mainpage.h
+++ b/doxygen/input/doc_mainpage.h
@@ -4,7 +4,7 @@
  */
 
 /**
- * @mainpage mbed TLS v1.3.14 source code documentation
+ * @mainpage mbed TLS v1.3.15 source code documentation
  *
  * This documentation describes the internal structure of mbed TLS.  It was
  * automatically generated from specially formatted comment blocks in