Re-point the tinycortex gitlink at the merged commit

tinycortex#149 landed as a squash (8401346b), discarding the branch head
this pin pointed at; 34cbb6c is diverged from tinycortex main rather than
an ancestor of it. The merged commit is also the one that deletes the 33
duplicated files under api/src/, which is the state this stack depends on.

Author: YellowSnnowmann