docs: removed references to `arcgis-rest-service-admin`

[gavinr-maps]

Removed all references to arcgis-rest-service-admin, which is an old package name that was replaced by arcgis-rest-feature-service. See here:

• https://github.com/Esri/arcgis-rest-js/pull/930
• https://github.com/Esri/arcgis-rest-js/issues/933

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (a801537) to head (d82fc68). Report is 30 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1152 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 177 177 Lines 3247 3247 Branches 551 551 ========================================= Hits 3247 3247 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.