Failover Cluster Diagnostic Logs
You can change this behavior with the ALTER SERVER CONFIGURATION statement.  The flexibility to modify all of the necessary parameters (path, max files, max file size) should give you enough control to get it to where you want.  See the bottom of the referenced link above for samples/examples.  Here is one copied from the source:

ALTER SERVER CONFIGURATION 
SET DIAGNOSTICS LOG MAX_SIZE = 10 MB;


HOWEVER ... these diagnostic logs are great tools for troubleshooting.  Whereas you can limit the amount of retained data, I would much rather get more storage to store the default amount of data (1000 MB, which is almost free in today's day) for the time when you will need as much diagnostic data as you can get.