disasm/exec/validate/wasm: trivial typo fixes

[justinclift]

Trivial typo fixes noticed while looking through the code base.

[codecov-io]

Codecov Report

Merging #132 into master will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #132   +/-   ##
=======================================
  Coverage   67.55%   67.55%           
=======================================
  Files          41       41           
  Lines        4787     4787           
=======================================
  Hits         3234     3234           
  Misses       1281     1281           
  Partials      272      272

Impacted Files	Coverage Δ
wasm/index.go	54.54% <ø> (ø)	:arrow_up:
exec/memory.go	86.32% <ø> (ø)	:arrow_up:
disasm/disasm.go	81.78% <ø> (ø)	:arrow_up:
wasm/section.go	49.28% <ø> (ø)	:arrow_up:

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[sbinet]

needs https://github.com/go-interpreter/license/pull/16.

[sbinet]

thanks!