Fix the doctests

Author: JamesWrigley

src/rules.jl

@@ -18,11 +18,11 @@ unary input, unary output scalar function:
 ```jldoctest frule
 julia> dself = NoTangent();
 
-julia> x = rand()
-0.8236475079774124
+julia> x = 1.23456
+1.23456
 
 julia> sinx, Δsinx = frule((dself, 1), sin, x)
-(0.7336293678134624, 0.6795498147167869)
+(0.9440031218347901, 0.3299365180851773)
 
 julia> sinx == sin(x)
 true
@@ -51,7 +51,7 @@ that return a single output that is iterable, like a `Tuple`.
 So this is actually a [`Tangent`](@ref):
 ```jldoctest frule
 julia> Δsincosx
-Tangent{Tuple{Float64, Float64}}(0.6795498147167869, -0.7336293678134624)
+Tangent{Tuple{Float64, Float64}}(0.3299365180851773, -0.9440031218347901)
 ```
 
 The optional [`RuleConfig`](@ref) option allows specifying frules only for AD systems that

src/tangent_types/thunks.jl

@@ -179,7 +179,7 @@ argument is not a `Thunk`.
 
 ```jldoctest
 julia> t = @thunk(3)
-Thunk(var"#4#5"())
+Thunk(var"#2#3"())
 
 julia> unthunk(t)
 3