Improve example_amazon_s3_snowflake_transform dag

[utkarsharma2]

Closes: #136

example_amazon_s3_snowflake_transform.py was using prepopulated tables in the snowflake database.

Removed dependency from prepopulated tables by using the load_file operator.

[codecov]

Codecov Report

Merging #293 (9738d32) into main (f9a50f4) will increase coverage by 0.22%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #293      +/-   ##
==========================================
+ Coverage   92.05%   92.27%   +0.22%     
==========================================
  Files          35       35              
  Lines        1535     1527       -8     
  Branches      268      268              
==========================================
- Hits         1413     1409       -4     
+ Misses         90       86       -4     
  Partials       32       32              

Impacted Files	Coverage Δ
src/astro/sql/operators/sql_decorator.py	92.14% <ø> (+0.86%)	⬆️
src/astro/sql/parsers/sql_directory_parser.py	94.39% <ø> (+1.59%)	⬆️

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