Remove bad generic sqrt method (#2068)

Method dispatch does not take keyword arguments into account. Therefore the kind of dispatch used by this method is risky and can result in an infinite recursion.

Author: fingolfin

src/Rings.jl

@@ -179,15 +179,6 @@ function Base.sqrt(a::FieldElem; check::Bool=true)
   error("Element $a does not have a square root")
 end
 
-# assumes the existence of sqrt without check argument for input
-function Base.sqrt(a::RingElem; check::Bool=true)
-  s = sqrt(a)
-  if check
-    s != a^2 && error("Element $a does not have a square root")
-  end
-  return s
-end  
-
 # assumes the existence of is_square and sqrt for input  
 function is_square_with_sqrt(a::RingElem)
   if is_square(a)