(documentation) rlet function parameters

[luavreis]

Hi,
The documentation for rlet states that it takes an expr as a parameter, but from my understanding it only takes a list of substitutions in a Dict or varargs in Pair form:

Reduce.jl/src/unary.jl

Lines 211 to 213 in fcc9459

	"""
	rlet(::Union{Dict,Pair},expr)

[luavreis]

By the way, in the same section, someone forgot to close a code environment in the docs for clear:

Reduce.jl/src/args.jl

Lines 1010 to 1016 in fcc9459

	The user may remove all assignments and substitution rules from any expression by the command `clear`, in the form
	```
	R"clear ⟨expression⟩,…,⟨expression⟩ = ⟨terminator⟩"
	e.g.
	```Julia
	julia> Algebra.clear(:x,:(h(x,y)))
	```

[chakravala]

Thanks, you are welcome to make a pull request next time and let me know of any other issues.