Bump linregress due to security vulnerability

[trevor-crypto]

https://rustsec.org/advisories/RUSTSEC-2021-0070

Here is the cargo deny failure:

    = Advisory: https://rustsec.org/advisories/RUSTSEC-2021-0070
    = The `Deserialize` implementation for `VecStorage` did not maintain the invariant that the number of elements must equal `nrows * ncols`. Deserialization of specially crafted inputs could allow memory access beyond allocation of the vector.
      
      This flaw was introduced in v0.11.0 ([`086e6e`](https://github.com/dimforge/nalgebra/commit/086e6e719f53fecba6dadad2e953a487976387f5)) due to the addition of an automatically derived implementation of `Deserialize` for `MatrixVec`. `MatrixVec` was later renamed to `VecStorage` in v0.16.13 ([`0f66403`](https://github.com/dimforge/nalgebra/commit/0f66403cbbe9eeac15cedd8a906c0d6a3d8841f2)) and continued to use the automatically derived implementation of `Deserialize`.
      
      This flaw was corrected in commit [`5bff536`](https://github.com/dimforge/nalgebra/commit/5bff5368bf38ddfa31416e4ae9897b163031a513) by returning an error during deserialization if the number of elements does not exactly match the expected size.
    = Announcement: https://github.com/dimforge/nalgebra/issues/883
    = Solution: Upgrade to >=0.27.1
    = nalgebra v0.26.2
      └── statrs v0.14.0
          └── linregress v0.4.2
              └── frame-benchmarking v3.1.0
                  └── pallet-balances v3.0.0

[cla-bot-2021]

User @trevor-crypto, please sign the CLA here.

[trevor-crypto]

I don't think I can add a label here, so can someone label this as "insubstantial" since it is only a dependency bump?