Remove documentation regarding MBEDTLS_GCM_ALT

MBEDTLS_GCM_ALT has been removed in the current version.

Signed-off-by: Harry Ramsey <harry.ramsey@arm.com>
diff --git a/tf-psa-crypto/drivers/builtin/include/mbedtls/gcm.h b/tf-psa-crypto/drivers/builtin/include/mbedtls/gcm.h
index 37d07d8..e620be7 100644
--- a/tf-psa-crypto/drivers/builtin/include/mbedtls/gcm.h
+++ b/tf-psa-crypto/drivers/builtin/include/mbedtls/gcm.h
@@ -174,9 +174,7 @@
  *
  * \note            The output buffer \p output can be the same as the input
  *                  buffer \p input. If \p output is greater than \p input, they
- *                  cannot overlap. Implementations which require
- *                  MBEDTLS_GCM_ALT //no-check-names to be enabled may not
- *                  provide support for overlapping buffers.
+ *                  cannot overlap.
  *
  * \param ctx       The GCM context. This must be initialized.
  * \param length    The length of the ciphertext to decrypt, which is also
@@ -284,9 +282,7 @@
  *
  * \note            The output buffer \p output can be the same as the input
  *                  buffer \p input. If \p output is greater than \p input, they
- *                  cannot overlap. Implementations which require
- *                  MBEDTLS_GCM_ALT //no-check-names to be enabled may not
- *                  provide support for overlapping buffers.
+ *                  cannot overlap.
  *
  * \param ctx           The GCM context. This must be initialized.
  * \param input         The buffer holding the input data. If \p input_length