fix(extension): missing extension in downloaded file

[lucasrodes]

Loading files from remote was not working because the temporary downloaded file to local was not saving the file with the appropriate extension. As a consequence, the proper loading pandas function was not being loaded.

[codecov]

Codecov Report

Merging #59 (890b070) into main (6cf53c7) will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #59      +/-   ##
==========================================
+ Coverage   89.13%   89.15%   +0.02%     
==========================================
  Files          18       18              
  Lines         782      784       +2     
==========================================
+ Hits          697      699       +2     
  Misses         85       85              

Impacted Files	Coverage Δ
owid/datautils/decorators.py	100.00% <100.00%> (ø)

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