Apply suggestions from code review

Co-authored-by: Eric Wolz <[email protected]>

Author: danewalton-msft

src/certs/readme.md

@@ -1,10 +1,10 @@
 ## Certificates -  Important to know
 
-The Azure IoT Hub certificates presented during TLS negotiation shall be always validated using the appropriate root CA certificate(s).
+The Azure IoT Hub certificates presented during TLS negotiation must be always validated using the appropriate root CA certificate(s).
 
 The samples in this repository leverage the certificates in `certs.c` for the United States, Germany sovereign cloud and China sovereign cloud.
 
-For other regions (and private cloud environments), please use the appropriate root CA certificate.
+For other regions (and private cloud environments), please use the appropriate root CA certificate of their IoT services endpoint.
 
 Always prefer using the local system's Trusted Root Certificate Authority store instead of hardcoding the certificates (i.e. using certs.c such as our samples require in certain combinations).