Explain why uninstall script needs admin password

[William-Laverty]

Summary

Fixes #1111

Adds an informative message to the uninstall script explaining why an administrator password is required before prompting for it.

Changes

Added a single line before the first sudo command:

This script requires an administrator password to remove the application files from system directories.

Before

% uninstall-container.sh -d
Password:

After

% uninstall-container.sh -d
This script requires an administrator password to remove the application files from system directories.
Password:

[jglogan]

@William-Laverty What is this one for when you already filed #1118?

See the comments about about commit signing in that PR.

[jglogan]

With #1118 merged and your #1130 for enhancing the message further, is this one needed or can you close it?

[William-Laverty]

Closing as redundant - #1118 was merged and #1130 covers the enhanced messaging. Thanks for the review!