Test: add space after test failure for visual clarity (#48526)

Author: IanButterworth

stdlib/Test/docs/src/index.md

@@ -55,6 +55,7 @@ julia> @test foo("f") == 20
 Test Failed at none:1
   Expression: foo("f") == 20
    Evaluated: 1 == 20
+
 ERROR: There was an error during testing
 ```
 
@@ -224,6 +225,7 @@ julia> @test 1 ≈ 0.999999
 Test Failed at none:1
   Expression: 1 ≈ 0.999999
    Evaluated: 1 ≈ 0.999999
+
 ERROR: There was an error during testing
 ```
 You can specify relative and absolute tolerances by setting the `rtol` and `atol` keyword arguments of `isapprox`, respectively,

stdlib/Test/src/Test.jl

@@ -165,6 +165,7 @@ function Base.show(io::IO, t::Fail)
             print(io, "\n     Context: ", t.context)
         end
     end
+    println(io) # add some visual space to separate sequential failures
 end
 
 """
@@ -1405,6 +1406,7 @@ julia> @testset let logi = log(im)
 Test Failed at none:3
   Expression: !(iszero(real(logi)))
      Context: logi = 0.0 + 1.5707963267948966im
+
 ERROR: There was an error during testing
 ```
 """