Fix typo

Author: erichaney

examples/-.janet

@@ -1,7 +1,7 @@
 (-) # -> 0
 (- 10) # -> -10
 (- 1 2) # -> -1
-(+ 1.4 -4.5) # -> 5.9
+(- 1.4 -4.5) # -> 5.9
 
 # Equivalent to (- first (+ ;rest))
 (- 1 2 3 4 5 6 7 8 9 10) # -> -53