docs(data): fix compilation errors in example

[LMFinney]

The example code for "Replace the HttpUrlGenerator" has two errors:

1. pluralizer is misspelled as pluralizzer once
2. pluralizer needs to be something else to avoid conflicting with the private pluralizer property in the parent.

PR Checklist

Please check if your PR fulfills the following requirements:

• [x ] The commit message follows our guidelines: https:/ngrx/platform/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ x] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

Compilation errors in a documentation example

Closes #

What is the new behavior?

Pasting the code into a project does not introduce a compilation error.

Does this PR introduce a breaking change?

[ ] Yes
[x ] No

Other information

[ngrxbot]

Preview docs changes for b998ee4 at https://previews.ngrx.io/pr2490-b998ee4/

[alex-okrushko]

Thanks :)

[timdeschryver]

Thanks @LMFinney !