fix requires-python

[wakamex]

according to python.org have to match version specifiers most recently defined by PEP 440
examples:

~=3.1: version 3.1 or later, but not version 4.0 or later.
~=3.1.2: version 3.1.2 or later, but not version 3.2.0 or later.
~=3.1a1: version 3.1a1 or later, but not version 4.0 or later.
== 3.1: specifically version 3.1 (or 3.1.0), excludes all pre-releases, post releases, developmental releases and any 3.1.x maintenance releases.
== 3.1.*: any version that starts with 3.1. Equivalent to the ~=3.1.0 compatible release clause.
~=3.1.0, != 3.1.3: version 3.1.0 or later, but not version 3.1.3 and not version 3.2.0 or later.

I was alerted to this by ruff which was correctly throwing an error:

error: TOML parse error at line 20, column 19
   |
20 | requires-python = "3.10"
   |                   ^^^^^^
Failed to parse version:
3.10
^^^^

PS: also noticed pip would throw a warning:

pip install -e .
Obtaining file:///code/elfpy
  Installing build dependencies ... done
  Checking if build backend supports build_editable ... done
  Getting requirements to build editable ... done
  Preparing editable metadata (pyproject.toml) ... done
WARNING: Package 'elfpy' has an invalid Requires-Python: Invalid specifier: '3.10'

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[sentilesdal]

looks good to me

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