Math::Trig: correct interval in documentation

This effectively undoes commit 02b54f9, which tried to fix a typo,
but introduced a technical inaccuracy because it wasn't a typo.

The intent is to specify a half-open interval including 0 but not
including 2pi. The original notation used was [a, b[ which is common in
some European countries, but [a, b) seems to be more common in the
English-speaking world.

Author: mauke

dist/Math-Complex/lib/Math/Trig.pm

@@ -425,7 +425,7 @@ and the imaginary part of approximately C<-1.317>.
 =back
 
 The full circle is 2 I<pi> radians or I<360> degrees or I<400> gradians.
-The result is by default wrapped to be inside the [0, {2pi,360,400}] circle.
+The result is by default wrapped to be inside the [0, {2pi,360,400}) circle.
 If you don't want this, supply a true second argument:
 
     $zillions_of_radians  = deg2rad($zillions_of_degrees, 1);