Bump version

./scripts/bump_version.sh --version 2.28.6 --so-crypto 7 --so-x509 1 --so-tls 14

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/doxygen/input/doc_mainpage.h b/doxygen/input/doc_mainpage.h
index 1a4cc41..c2343a6 100644
--- a/doxygen/input/doc_mainpage.h
+++ b/doxygen/input/doc_mainpage.h
@@ -10,7 +10,7 @@
  */
 
 /**
- * @mainpage Mbed TLS v2.28.5 API Documentation
+ * @mainpage Mbed TLS v2.28.6 API Documentation
  *
  * This documentation describes the internal structure of Mbed TLS.  It was
  * automatically generated from specially formatted comment blocks in