Fixed docblock for htmlEncode and htmlDecode [skip ci]
Merge pull request #6331 from nikbas/arrayhelper-doc-fix

[skip ci] Fix docblock in ArrayHelper
docs/internals-ja/design-decisions.md - added [ci skip]
docs/guide-ja/README.md - updated [ci skip]
docs/guide-ja/start-installation.md - updated [ci skip]
Merge pull request #6333 from softark/docs-guide-ja-update

Docs guide/internals ja update [ci skip]