refactor(basis): remove unused NURBS recursion stub

Drop standalone nurbs.jl helper not wired into the current basis pipeline.

src/basis/nurbs.jl

@@ -1,16 +0,0 @@
-# This file is a part of JuliaFEM.
-# License is MIT: see https://github.com/JuliaFEM/jl/blob/master/LICENSE
-
-import Base: size, length
-
-function NURBS(i, p, u, t)
-    p == 0 && return t[i] <= u <= t[i+1] ? 1.0 : 0.0
-    anom = u-t[i]
-    adenom = t[i+p]-t[i]
-    a = isapprox(adenom, 0.0) ? 0.0 : anom/adenom
-    bnom = t[i+p+1]-u
-    bdenom = t[i+p+1]-t[i+1]
-    b = isapprox(bdenom, 0.0) ? 0.0 : bnom/bdenom
-    result = a*NURBS(i,p-1,u,t) + b*NURBS(i+1,p-1,u,t)
-    return result
-end