workflow: remove tech leads

Author: 0xc0170

docs/reference/contributing/guidelines/workflow.md

@@ -27,15 +27,6 @@ The current maintainers are:
 * [Sam Grove](https://os.mbed.com/users/sam_grove).
 * [Cruz Monrreal](https://os.mbed.com/users/MrCruz).
 
-##### Mbed OS tech leads
-
-They are responsible for specific Mbed OS modules or features.
-
-Responsibilities:
-
-1. Review pull requests and coordinate reviews within the team.
-1. Ensure the version label is correct.
-
 #### Contributions
 
 Before contributing an enhancement (new feature, new port and so on), please [discuss it on the forums](https://os.mbed.com/forum/bugs-suggestions/) to avoid duplication of work, as we or others might be working on a related feature.