Fix failing windows test

[ejm714]

Use non-interactive backend in CI for Matplotlib to resolve Windows error

FAILED tests/test_evaluate.py::test_calculate_all_and_save - _tkinter.TclError: Can't find a usable init.tcl in the following directories: 
    {C:\hostedtoolcache\windows\Python\3.10.11\x64\tcl\tcl8.6}

C:/hostedtoolcache/windows/Python/3.10.11/x64/tcl/tcl8.6/init.tcl: couldn't read file "C:/hostedtoolcache/windows/Python/3.10.11/x64/tcl/tcl8.6/init.tcl": No error
couldn't read file "C:/hostedtoolcache/windows/Python/3.10.11/x64/tcl/tcl8.6/init.tcl": No error
    while executing
"source C:/hostedtoolcache/windows/Python/3.10.11/x64/tcl/tcl8.6/init.tcl"
    ("uplevel" body line 1)
    invoked from within
"uplevel #0 [list source $tclfile]"


This probably means that Tcl wasn't installed properly.

Closes #168

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.6%. Comparing base (768b622) to head (41ebca4).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main    #169     +/-   ##
=======================================
- Coverage   79.3%   74.6%   -4.7%     
=======================================
  Files         12      12             
  Lines        875     875             
=======================================
- Hits         694     653     -41     
- Misses       181     222     +41     

see 2 files with indirect coverage changes

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[jayqi]

TWIL: https://matplotlib.org/stable/users/explain/figure/backends.html