Docs updates for E/A#97094 Show GL codes in tag picker setting

[MelvinBot]

Help site update for E/A#97094

PR #97094 adds a Show GL codes when selecting a tag toggle in Workspaces > [workspace name] > Tags > Settings (Control plan, visible only when GL codes are enabled). When on, each tag's GL code appears as a muted second line under the tag name in the tag picker, and members can search tags by GL code.

This changes previously documented behavior: the help article stated that tag GL codes are not visible to members. That is now conditional.

Changes

Updated docs/articles/new-expensify/workspaces/Create-and-manage-expense-tags.md:

• Added a new section How to show tag GL codes when selecting a tag describing the toggle and its effect.
• Updated the How to add or edit a tag GL code intro note to reflect that GL codes can now be shown in the tag picker.
• Updated the FAQ Can members see Tag GL codes? to explain the new setting.

Notes for reviewer

• Feature name, toggle label (Show GL codes when selecting a tag), and the Tags > Settings navigation were taken from the source PR's copy (src/languages/en.ts) and the existing help-site navigation conventions. A live-UI verification pass could not complete because the test session lost authentication — please confirm the toggle label and location against the current UI.
• Backend dependency: the source PR notes the SetPolicyShowTagGLCodes backend command is not yet deployed, so enabling the toggle currently rolls back with an error. This PR is left as a draft until the feature is fully live in production.

Kept as a draft pending the review below.

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@neerajbachani, please review the files changed and confirm they reflect the current behavior. Then post a new comment saying @MelvinBot mark this PR as ready for review.