DHM functions are not part of x509

In the old days, key parsing was part of x509, but these days it's
part of crypto.
diff --git a/include/mbedtls/dhm.h b/include/mbedtls/dhm.h
index 9890e0c..6dcfadd 100644
--- a/include/mbedtls/dhm.h
+++ b/include/mbedtls/dhm.h
@@ -298,7 +298,6 @@
 void mbedtls_dhm_free( mbedtls_dhm_context *ctx );
 
 #if defined(MBEDTLS_ASN1_PARSE_C)
-/** \ingroup x509_module */
 /**
  * \brief             This function parses DHM parameters in PEM or DER format.
  *
@@ -317,7 +316,6 @@
                            size_t dhminlen );
 
 #if defined(MBEDTLS_FS_IO)
-/** \ingroup x509_module */
 /**
  * \brief          This function loads and parses DHM parameters from a file.
  *