fix -Wabsolute-value compiler warning

fixes:
Clock.c:2011:14: warning: using integer absolute value function ‘abs’ when argument is of floating-point type ‘float’ [-Wabsolute-value]
 2011 |             (abs(new->clock.update) <= SECOND_HAND_TIME);
      |              ^~~
6 jobs for compiler_warnings in 25 seconds (queued for 7 seconds)
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