fix(deps): update dependency koa-session to v5.13.1

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
koa-session	dependencies	minor	5.12.3 -> 5.13.1

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Release Notes

koajs/session

### [`v5.13.1`](https://togithub.com/koajs/session/blob/master/History.md#​5131--2020-02-01) [Compare Source](https://togithub.com/koajs/session/compare/5.13.0...5.13.1) ================== **fixes** - \[[`ecd1f5e`](http://github.com/koajs/session/commit/ecd1f5edaa6ff1e77cc461d1107432b394ce21d2)] - fix: don't set any value to sameSite by default ([#​194](https://togithub.com/koajs/session/issues/194)) (fengmk2 >) ### [`v5.13.0`](https://togithub.com/koajs/session/blob/master/History.md#​5130--2020-02-01) [Compare Source](https://togithub.com/koajs/session/compare/5.12.3...5.13.0) ================== **features** - \[[`cb09a09`](http://github.com/koajs/session/commit/cb09a09cfa4767610d7cc7282a0de2a3a651c6ae)] - feat: support session cookie sameSite options ([#​193](https://togithub.com/koajs/session/issues/193)) (fengmk2 >)

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Branch automerge failure

This PR was configured for branch automerge, however this is not possible so it has been raised as a PR instead.

[coveralls]

Coverage remained the same at 80.638% when pulling 30fb32dc3c2af30286c991355fd4fb82b540439e on renovate/koa-session-5.x into 69475abb32f16c9418273f12af4988571dee2bfd on master.