Bump version to Mbed TLS 2.23.0

Executed "./scripts/bump_version.sh --version 2.23.0 --so-crypto 5"

A symbol has been removed from the mbedcrypto library since the last
release:
mbedtls_ecc_group_to_psa ( enum mbedtls_ecp_group_id grpid,
                           size_t* bits )

This is an ABI break and we need to increase the SO version.

Signed-off-by: Janos Follath <janos.follath@arm.com>
diff --git a/doxygen/input/doc_mainpage.h b/doxygen/input/doc_mainpage.h
index 749d5c1..27a840a 100644
--- a/doxygen/input/doc_mainpage.h
+++ b/doxygen/input/doc_mainpage.h
@@ -24,7 +24,7 @@
  */
 
 /**
- * @mainpage mbed TLS v2.22.0 source code documentation
+ * @mainpage mbed TLS v2.23.0 source code documentation
  *
  * This documentation describes the internal structure of mbed TLS.  It was
  * automatically generated from specially formatted comment blocks in