use native Julia code in round example (#46841)

Author: udohjeremiah

base/floatfuncs.jl

@@ -99,12 +99,12 @@ julia> round(357.913; sigdigits=4, base=2)
     value represented by `1.15` is actually *less* than 1.15, yet will be
     rounded to 1.2. For example:
 
-    ```jldoctest; setup = :(using Printf)
+    ```jldoctest
     julia> x = 1.15
     1.15
 
-    julia> @sprintf "%.20f" x
-    "1.14999999999999991118"
+    julia> big(1.15)
+    1.149999999999999911182158029987476766109466552734375
 
     julia> x < 115//100
     true