dstat.tests: Replace usage of approxEqual with isClose in non-test code

approxEqual is deprecated, isClose is the replacement.
approxEqual is still widely used in tests,
but tat least this won't trigger deprecations
in client code.

Author: Geod24

source/dstats/tests.d

@@ -1941,7 +1941,7 @@ double binomialTest(ulong k, ulong n, double p) {
 
     immutable mode = cast(long) ((n + 1) * p);
     if(k == mode ||
-       approxEqual(binomialPMF(k, n, p), binomialPMF(mode, n, p), 1 - epsilon)) {
+       isClose(binomialPMF(k, n, p), binomialPMF(mode, n, p), 1 - epsilon, 1e-5)) {
         return 1;
     } else if(k > mode) {
         immutable double upperPart = binomialCDFR(k, n, p);