perf: avoid update when expanding same node

[jledentu]

This PR early returns when update tries to expand the already expanded node

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (9455989) 99.42% compared to head (3b6d894) 99.43%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## 2.x #207 +/- ## ======================================= Coverage 99.42% 99.43% ======================================= Files 4 4 Lines 175 177 +2 Branches 44 45 +1 ======================================= + Hits 174 176 +2 Misses 1 1 ``` | [Impacted Files](https://app.codecov.io/gh/jledentu/vue-finder/pull/207?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=J%C3%A9r%C3%A9mie+Ledentu) | Coverage Δ | | |---|---|---| | [src/utils/tree-model.js](https://app.codecov.io/gh/jledentu/vue-finder/pull/207?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=J%C3%A9r%C3%A9mie+Ledentu#diff-c3JjL3V0aWxzL3RyZWUtbW9kZWwuanM=) | `99.20% <100.00%> (+0.01%)` | :arrow_up: |

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[github-actions[bot]]

:tada: This PR is included in version 2.1.2 :tada:

The release is available on:

• npm package (@release-2.x dist-tag)
• GitHub release

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