fix trailing newline parse bug

[charles-cooper]

What I did

Fix #2410

The previous fix in #1720 stopped working because the modified source
code was only being provided to some compilation steps (compile_codes)
but not others (get_interface_codes).

How I did it

Move the additional newline upstream

How to verify it

Compile the code in the issue

Description for the changelog

Cute Animal Picture

[codecov-commenter]

Codecov Report

Merging #2412 (256e568) into master (b52715e) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2412      +/-   ##
==========================================
+ Coverage   85.47%   85.51%   +0.03%     
==========================================
  Files          91       91              
  Lines        9034     9034              
  Branches     2151     2151              
==========================================
+ Hits         7722     7725       +3     
+ Misses        806      804       -2     
+ Partials      506      505       -1     

Impacted Files	Coverage Δ
vyper/cli/vyper_compile.py	75.00% <100.00%> (ø)
vyper/compiler/__init__.py	85.71% <100.00%> (ø)
vyper/old_codegen/arg_clamps.py	100.00% <0.00%> (ø)
vyper/builtin_functions/functions.py	88.68% <0.00%> (+0.36%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update b52715e...256e568. Read the comment docs.