Fix typos prior to release

Signed-off-by: Tom Cosgrove <tom.cosgrove@arm.com>
diff --git a/library/x509_crl.c b/library/x509_crl.c
index 624bff1..b943a8d 100644
--- a/library/x509_crl.c
+++ b/library/x509_crl.c
@@ -1,5 +1,5 @@
 /*
- *  X.509 Certidicate Revocation List (CRL) parsing
+ *  X.509 Certificate Revocation List (CRL) parsing
  *
  *  Copyright The Mbed TLS Contributors
  *  SPDX-License-Identifier: Apache-2.0