Remove reference to "denorms are flushed to zero"

This appears to be an error from when we transcribed these function
definitions from OpenCL.  There is no mode called "denorms are flushed
to zero" in SYCL.  In OpenCL, this corresponds to the compiler flag
"-cl-denorms-are-zero", but SYCL does not define any compiler flags.

Vendors could define a compiler flag like this if they want.  In this
case, it would be the vendor's responsibility to document the effect.

Closes internal issue 657.

adoc/chapters/programming_interface.adoc

@@ -25659,9 +25659,6 @@ with the following exceptions:
     value of the floating-point values in the result vector are undefined.
   . If the sum of squares is less than [code]#FLT_MIN# then the
     implementation may return back [code]#p#.
-  . If the device is in "`denorms are flushed to zero`" mode, individual
-    operand elements with magnitude less than [code]#sqrt(FLT_MIN)# may
-    be flushed to zero before proceeding with the calculation.
 --
 
 The return type is [code]#GeoFloat# unless [code]#GeoFloat# is the