Remove unneeded (mistaken) object return in processing level decorator function

[emiliom]

For echodata class methods, the decorator wrapper-inner function was returning self, when in fact no return statement was necessary. This had no harmful effect per se, that I can see, but it was effectively "printing out" the echodata object. This effect was visible when running echodata.update_platform in a Jupyter notebook.

I'll self merge. This is a simple change (removed return self statement) to code I wrote for the last release.

[codecov-commenter]

Codecov Report

Merging #1037 (7045efe) into dev (f5e5b3c) will decrease coverage by 0.32%.
The diff coverage is n/a.

📣 This organization is not using Codecov’s GitHub App Integration. We recommend you install it so Codecov can continue to function properly for your repositories. Learn more

@@            Coverage Diff             @@
##              dev    #1037      +/-   ##
==========================================
- Coverage   80.71%   80.40%   -0.32%     
==========================================
  Files          67        5      -62     
  Lines        6057      444    -5613     
==========================================
- Hits         4889      357    -4532     
+ Misses       1168       87    -1081     

Flag	Coverage Δ
unittests	80.40% <ø> (-0.32%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
echopype/utils/prov.py	92.55% <ø> (-1.14%)	⬇️

... and 65 files with indirect coverage changes

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more