Revert "Feature: Allow getting credentials via EC2 role (#3343)" (#3985)
Revert "Feature: Allow getting credentials via EC2 role (#3343)" (#3985)

This reverts commit 808f79f00aab29cd6464c71b120105765533c4c7.
GoogleCloudPlatform/prometheus,alileza/prometheus,prometheus/prometheus,GoogleCloudPlatform/prometheus,kangwoo/prometheus,GoogleCloudPlatform/prometheus,GoogleCloudPlatform/prometheus,keegancsmith/prometheus,Gouthamve/prometheus,alileza/prometheus,Gouthamve/prometheus,Gouthamve/prometheus,alileza/prometheus,keegancsmith/prometheus,amorken/prometheus,GoogleCloudPlatform/prometheus,alileza/prometheus,kangwoo/prometheus,prometheus/prometheus,alileza/prometheus,amorken/prometheus,prometheus/prometheus,amorken/prometheus,kangwoo/prometheus,Gouthamve/prometheus,keegancsmith/prometheus,prometheus/prometheus,kangwoo/prometheus,prometheus/prometheus,keegancsmith/prometheus,amorken/prometheus,keegancsmith/prometheus