[#397] Remove `parse` from `morley`

Description

Problem: morley executable has parse command that parses a smart contract and prints its Haskell representation. It was useful at early development, for example to test our parser, but now it seems quite useless, I doubt anybody used it recently. We can test parser by other means, e. g. using print (it parses the source contract). By removing this command we can drop the pretty-simple dependency which is used only there apparently.

Solution: remove this command and pretty-simple dependency.

Related issue(s)

Resolves #397 (closed)

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