Fix comment

Author: devmotion

test/generics.jl

@@ -23,7 +23,7 @@ for i in 1:length(pmats)
     @test Matrix(pmats[i] * 3)   == Matrix(pmatsa[i])
 end
 
-# issue #123
+# issue #121
 @test isposdef(PDMat([1.0 0.0; 0.0 1.0]))
 @test isposdef(PDiagMat([1.0, 1.0]))
 @test isposdef(ScalMat(2, 3.0))