R1:9bc3c16b6e75

Fix information page about Read-only status

Summary:
This change fixes the following page on your Phorge/Phabricator:

/readonly/config/

If you visit that page (with or without read-only mode), the
following crash will happen:

Call to undefined method PlatformSymbols::getPlatformServerSymbol()

Fixes T15185

Probably the regression was introduced in this point:

rP4d3f0dc7c727e6fdc0e8cba0e8e8f2b8ef1bd16c

This change also renamed "administrator" to "Administrator" in the messages
from that…