Minor documentation improvements

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/include/psa/crypto_platform.h b/include/psa/crypto_platform.h
index 17ebd70..8acf22c 100644
--- a/include/psa/crypto_platform.h
+++ b/include/psa/crypto_platform.h
@@ -82,7 +82,7 @@
 #endif /* MBEDTLS_PSA_CRYPTO_KEY_ID_ENCODES_OWNER */
 
 #if defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
-/** The type of contexts passed to mbedtls_psa_external_get_random().
+/** The type of the context passed to mbedtls_psa_external_get_random().
  *
  * Mbed TLS initializes the context to all-bits-zero before calling
  * mbedtls_psa_external_get_random() for the first time.