Modify _totuple

[Yue-Zhengyuan]

This PR catches the edge case tensorexpr(:name, :i, :j) so it can be converted to tensorexpr(:name, (:i,), (:j,)) correctly.

julia> tuple(:a)
(:a,)

julia> Tuple(:a)
ERROR: MethodError: no method matching length(::Symbol)
The function `length` exists, but no method is defined for this combination of argument types.
...

See also QuantumKitHub/PEPSKit.jl#268.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
src/utility/utility.jl	75.94% <100.00%> (ø)

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[Yue-Zhengyuan]

@lkdvos Shall we bump the version so PEPSKit can start using it?

[Yue-Zhengyuan]

@lkdvos Can you help with bumping the version and releasing it? I don't quite know how it's done, and might mess up the release notes or something else...

[lkdvos]

Sure! For future reference, it's just a matter of typing the magic words in the comments of a particular commit, so typically I like to bump the version either via PR or directly and then type the magic words, see: ef1beb4

There it does suggest to add release notes, which I typically like to do but there are no strong rules about this. I don't think it was necessary here as _totuple really is an internal function anyways.