Remove broken doxygen link to internal macro

Removes a broken doxygen link to a macro that is now internal and
cannot be seen from the public API anymore.

Signed-off-by: Chris Jones <christopher.jones@arm.com>
diff --git a/include/psa/crypto_extra.h b/include/psa/crypto_extra.h
index 9abce33..8d98190 100644
--- a/include/psa/crypto_extra.h
+++ b/include/psa/crypto_extra.h
@@ -297,7 +297,7 @@
  * \param[in] seed          Buffer containing the seed value to inject.
  * \param[in] seed_size     Size of the \p seed buffer.
  *                          The size of the seed in bytes must be greater
- *                          or equal to both #MBEDTLS_ENTROPY_MIN_PLATFORM
+ *                          or equal to both MBEDTLS_ENTROPY_MIN_PLATFORM
  *                          and #MBEDTLS_ENTROPY_BLOCK_SIZE.
  *                          It must be less or equal to
  *                          #MBEDTLS_ENTROPY_MAX_SEED_SIZE.