replacing deprecated in1d, using ravel for scalars

[quant12345]

Please confirm that this PR has done the following:

• Tests Added
• Documentation Added
• Name of contributors Added to AUTHORS.rst
• Description in RELEASE_NOTES.md Added

Description of PR

Removes the warnings:

D:\a\pyam\pyam\pyam\plotting.py:230: DeprecationWarning: `in1d` is deprecated. Use `np.isin` instead.
    overlap_idx = np.in1d(values, list(PYAM_COLORS.keys()))

tests to check isin:

pytest tests/test_plotting.py::test_line_plot_cmap_color_arg
pytest tests/test_plotting.py::test_line_color
pytest tests/test_plotting.py::test_line_PYAM_COLORS
pytest tests/test_plotting.py::test_line_color_fill_between
pytest tests/test_plotting.py::test_line_color_fill_between_interpolate
pytest tests/test_plotting.py::test_line_color_final_ranges
pytest tests/test_plotting.py::test_line_filter_title
pytest tests/test_plotting.py::test_line_update_rc
pytest tests/test_plotting.py::test_scatter_variables_with_meta_color

  D:\a\pyam\pyam\pyam\timeseries.py:133: DeprecationWarning: Conversion of an array with ndim > 0 to a scalar is deprecated, and will error in future. Ensure you extract a single element from your array before performing this operation. (Deprecated NumPy 1.25.)
    return [y + 1 for y in map(int, years)]

tests to check scalar:

pytest tests/test_timeseries.py::test_cross_treshold
pytest tests/test_timeseries.py::test_cross_treshold_from_below
pytest tests/test_timeseries.py::test_cross_treshold_from_above

1. np.in1d is replaced by np.isin.

2. To get scalar values ​​during iteration I made the years array flat having applied ravel().
   The years values ​​have an extra dimension, which is why there is a warning:

[[2006.]
 [2010.]]

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.0%. Comparing base (ddbb88e) to head (71ab0e8).
Report is 33 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #882   +/-   ##
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  Coverage   95.0%   95.0%           
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  Files         64      64           
  Lines       6134    6216   +82     
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+ Hits        5828    5910   +82     
  Misses       306     306           

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