nit: describe the root program id

[jackcmay]

Problem

The variable name described as being the "loader's id" when its always a program but may not be a loader

Summary of Changes

Refer to it as the root program where its the root of a chain of programs >= 1 long

For example: could be the stake program -> |, or could be the BPFLoader -> program -> |

Fixes #

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@4f05f08). Click here to learn what that means.
The diff coverage is 100%.

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