removing cuda dependency from atomics test and fixing histogram example

Author: leios

examples/histogram.jl

@@ -1,6 +1,10 @@
 using KernelAbstractions, Test
 include(joinpath(@__DIR__, "utils.jl")) # Load backend
 
+if Base.VERSION < v"1.7.0"
+    return
+end
+
 # Function to use as a baseline for CPU metrics
 function create_histogram(input)
     histogram_output = zeros(Int, maximum(input))

test/atomic_test.jl

@@ -1,4 +1,4 @@
-using KernelAbstractions, CUDA, Test
+using KernelAbstractions, Test
 
 # Note: kernels affect second element because some CPU defaults will affect the
 #       first element of a pointer if not specified, so I am covering the bases