docs: EXPOSED-626 fix nullTransform example code

[kdhyo]

Description

Fixes a bug in the example code for nullTransform provided in the documentation.

Detailed description:

• What:
  Fix Docs Example code
• Why:
  If you try to use the example code as is, you'll get a compiler error.
• How:
  Change transform() to nullTransform().

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Type of Change

Please mark the relevant options with an "X":

• Bug fix
• New feature
• Documentation update

Updates/remove existing public API methods:

• Is breaking change

Affected databases:

• MariaDB
• Mysql5
• Mysql8
• Oracle
• Postgres
• SqlServer
• H2
• SQLite

Checklist

• Unit tests are in place
• The build is green (including the Detekt check)
• All public methods affected by my PR has up to date API docs
• Documentation for my change is up to date

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Related Issues

[bog-walk]

Thanks for starting this PR @kdhyo

Please see suggested changes in YouTrack issue and please apply them to the documentation-website file directly, instead of this .html file.

[bog-walk]

Thanks for the changes @kdhyo
All website and api docs are auto-synced with each release (aimed for the end of each month). So your changes will become visible then.