Update secure-boot.md (#1560)

Fixed a link in the end that wasn't rendering propely

Author: jhansson-ard

content/hardware/04.pro/boards/portenta-h7/tutorials/secure-boot/secure-boot.md

@@ -75,4 +75,4 @@ arduino-cli compile -b arduino:mbed_portenta:envie_m7 --board-options security=s
 ```
 
 ## Learn More
-If you want to implement secure boot for your platform, have a look at [this article] (https://arduino.github.io/arduino-cli/latest/guides/secure-boot/).
+If you want to implement secure boot for your platform, have a look at [this article](https://arduino.github.io/arduino-cli/latest/guides/secure-boot/).