DEP: special: Remove special.btdtr and special.btdtri (#21773)

* TST: special: remove tests for special.btdtr and special.btdtri

* DEP: special: remove code and references to special.btdtr and special.btdtri

* DEP: special: Remove deprecating message

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Co-authored-by: Daniel Schmitz <[email protected]>

Author: 2 people

scipy/special/xsf/stats.h

@@ -22,10 +22,6 @@ inline double bdtri(double k, int n, double y) { return cephes::bdtri(k, n, y);
 
 inline double bdtrc(double k, int n, double p) { return cephes::bdtrc(k, n, p); }
 
-inline double btdtri(double aa, double bb, double yy0) { return cephes::incbi(aa, bb, yy0); }
-
-inline double btdtr(double a, double b, double x) { return cephes::incbet(a, b, x); }
-
 inline double chdtr(double df, double x) { return cephes::chdtr(df, x); }
 
 inline double chdtrc(double df, double x) { return cephes::chdtrc(df, x); }