Ensure right fit object is in R scope

[sagar87]

PR Checklist

• Referenced issue is linked
• If you've fixed a bug or added code that should be tested, add tests!
• Documentation in docs is updated

Description of changes

This is a little fix to ensure that the right fit object is present in the R environment. This can cause issues if the user creates multiple EdgR objects and doesn't calculate contrasts immediately after fitting the object.

Technical details

N/A

Additional context

N/A

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 79.45%. Comparing base (0c429c5) to head (f19dc35).

Files with missing lines	Patch %	Lines
...rtpy/tools/_differential_gene_expression/_edger.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1073      +/-   ##
==========================================
- Coverage   79.46%   79.45%   -0.02%     
==========================================
  Files          53       53              
  Lines        7545     7546       +1     
==========================================
  Hits         5996     5996              
- Misses       1549     1550       +1     

Files with missing lines	Coverage Δ
...rtpy/tools/_differential_gene_expression/_edger.py	16.66% <0.00%> (-0.26%)	⬇️

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