fix(encoding): form decode field mask from well-know

[acynothia]

No description provided.

[codecov-commenter]

Codecov Report

Merging #2285 (7a39719) into main (2d20607) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 7a39719 differs from pull request most recent head 74ef702. Consider uploading reports for the commit 74ef702 to get more accurate results

@@           Coverage Diff           @@
##             main    #2285   +/-   ##
=======================================
  Coverage   85.17%   85.17%           
=======================================
  Files          88       88           
  Lines        3783     3783           
=======================================
  Hits         3222     3222           
  Misses        389      389           
  Partials      172      172           

Impacted Files	Coverage Δ
encoding/form/proto_decode.go	54.22% <100.00%> (ø)

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