Remove benjy as maintainer for Block subsystem

Removed benjy’s name and contact details from the MAINTAINERS.txt list. Now some core maintainer can merge the changes and notify the Core Committers Slack channel.

Confirmed that this MR would remove Benjy's contact details from the MAINTAINERS.txt.

xjm → credited benjy → .

Thanks @benjy for all your contributions!

Committed to 11.x and cherry-picked to 11.2.x, 10.6.x, and 10.5.x. I also removed permissions from the core project node and the maintainers channel.

xjm → closed merge request !12648

xjm → changed the visibility of the branch 3534386-remove-benjy-as to hidden.

Automatically closed - issue fixed for 2 weeks with no activity.