fix: pass scalar as series to update group information

[Unnamed-1408]

Attempt at fix for issue https://github.com/pola-rs/polars/issues/15183. The scalar variables are passed in as series to update groups information, which leads to panic in ac.groups(). https://github.com/pola-rs/polars/blob/252702a8c7f5c00558d2dc58460e2d9b41828917/crates/polars-lazy/src/physical_plan/expressions/apply.rs#L438 Therefore, resetting update_groups can solve this problem. Now, it works smoothly

>>> import polars as pl
>>> dfBug = (
...     pl.DataFrame({"a": [1, 2, 3, 4, 5, 2, 3, 5, 1], "b": [1, 2, 3, 1, 2, 3, 1, 2, 3]})
...     .group_by("a")
...     .agg(pl.col.b.unique().sort().str.concat("-").str.split("-"))
... )
>>> print(dfBug)
shape: (5, 2)
┌─────┬────────────┐
│ a   ┆ b          │
│ --- ┆ ---        │
│ i64 ┆ list[str]  │
╞═════╪════════════╡
│ 1   ┆ ["1", "3"] │
│ 2   ┆ ["2", "3"] │
│ 4   ┆ ["1"]      │
│ 3   ┆ ["1", "3"] │
│ 5   ┆ ["2"]      │
└─────┴────────────┘

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 81.32%. Comparing base (2fca551) to head (24911fd). Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #15271   +/-   ##
=======================================
  Coverage   81.31%   81.32%           
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  Files        1359     1359           
  Lines      176083   176077    -6     
  Branches     2524     2526    +2     
=======================================
+ Hits       143188   143189    +1     
+ Misses      32411    32404    -7     
  Partials      484      484           

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[ritchie46]

Thanks for the PR. I will clsoe this as the bug is resolved on main.