Bump simplicity-lang version to 0.7.1

[KyrylR]

So we can have a fix in SimplicityHL

[apoelstra]

I don't see why this is needed -- we already released simplicity-sys 0.6.1 with the fix.

[KyrylR]

For me to use the fix, for example in simplicity-contracts, I would have to have the following Cargo.toml:

[workspace.dependencies]
ring = "0.17.14"
sha2 = { version = "0.10.9", features = ["compress"] }

hex = "0.4.3"
tracing = { version = "0.1.41" }

simplicityhl = { version = "0.4.0" }
simplicityhl-core = { version = "0.3.2", features = ["encoding"] }

[patch.crates-io]
simplicity-sys = { git = "https://github.com/BlockstreamResearch/rust-simplicity", tag = "simplicity-sys-0.6.1" }

However, if we update and publish the new versions of rust-simplicity and simplicityhl, we will have the fix in the latest version, so people who do not know about the bug will not have to add the following line:

[patch.crates-io]
simplicity-sys = { git = "https://github.com/BlockstreamResearch/rust-simplicity", tag = "simplicity-sys-0.6.1" }

[KyrylR]

I believe we can bump the version after #337 is fixed

[apoelstra]

For me to use the fix, for example in simplicity-contracts, I would have to have the following Cargo.toml:

Why is cargo update -p simplicity-sys not sufficient?