kernel: suppress libsemigroups reporting by default

[james-d-mitchell]

@cdwensley I think this should fix the issue you reported to me by email today:

Some of the Groupoids tests have suddenly coming up with unexpected output such as:

#0: FroidurePin: enumerating until all elements are found . . .
#0: FroidurePin: ⌀ 1    (Cayley graph) | 3           (elements) | 0         (rules) | 41ns    (total)  
#0: FroidurePin: ⌀ 2    (Cayley graph) | 6           (elements) | 6         (rules) | 549µs   (total)  
#0: FroidurePin: ⌀ 3    (Cayley graph) | 10          (elements) | 7         (rules) | 555µs   (total)  
#0: FroidurePin: ⌀ 4    (Cayley graph) | 12          (elements) | 10        (rules) | 558µs   (total)  
#0: FroidurePin: ⌀ 5    (Cayley graph) | 13          (elements) | 11        (rules) | 569µs   (total)  
#0: FroidurePin:  #0: FroidurePin: number of products was  21 of 39 (53.846%)

and

FroidurePin: enumerating until ~8,195 elements are found
#0: FroidurePin: running until predicate returns true or finished
#0: FroidurePin: ⌀ 1    (Cayley graph) | 3           (elements) | 0         (rules) | 42ns    (total)  
#0: FroidurePin: ⌀ 2    (Cayley graph) | 11          (elements) | 1         (rules) | 13µs    (total)  
#0: FroidurePin: ⌀ 3    (Cayley graph) | 17          (elements) | 17        (rules) | 19µs    (total)  
#0: FroidurePin:  #0: FroidurePin: number of products was  37 of 51 (72.549%)

[cdwensley]

I daresay this would fix things, but I have no idea how to clone this fork. Sorry.