doc: Fixed notes formatting

Fixed the style used to format notes.

Signed-off-by: Francesco Servidio <francesco.servidio@nordicsemi.no>
diff --git a/docs/testplan-mynewt.md b/docs/testplan-mynewt.md
index 0e5e94f..402a493 100644
--- a/docs/testplan-mynewt.md
+++ b/docs/testplan-mynewt.md
@@ -22,11 +22,16 @@
 * `newt create-image k64f_blinky 1.0.1 key_<sign-algo>.pem`
 * `newt load k64f_blinky`
 
-NOTE: If testing RSA/PSS `newt create-image` needs to be passed in the extra
-flag `--rsa-pss` eg:
+---
+***Note***
+
+*If testing RSA/PSS `newt create-image` needs to be passed in the extra*
+*flag `--rsa-pss` eg:*
 
 `newt create-image k64f_blinky 1.0.1 key_rsa.pem --rsa-pss`
 
+---
+
 Build and load image in slot 1 with no signing, signed with
 key_<sign-algo>_2.pem and signed with key_<sign-algo>.pem. Mark each one as
 test image and check that swap only happens for image signed with