expr: fixed limit/series incorrect simplification, added regression test

[Qaaee123]

using ratsimp on s1 in series to provide correct simplified solution

References to other Issues or PRs

Fixes #9173

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• core
  • used ratsimp to proper display simplified series output. Before, would output incredibly complex series. Now, outputs correct simplified series.

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• core
  • used ratsimp to proper display simplified series output. Before, would output incredibly complex series. Now, outputs correct simplified series. (#26544 by @Qaaee123)

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using ratsimp on s1 in series to provide correct simplified solution

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Fixes #9173

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- core
  - used ratsimp to proper display simplified series output. Before, would output incredibly complex series. Now, outputs correct simplified series.

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[oscarbenjamin]

I'm not sure about calling ratsimp here. If we want to canonicalise the form of the output then it should be done systematically and that really means using ringseries I think.