Updaed yaml.load(file) to yaml.safe_load(file).

[davidraker]

Description

Replaces yaml.load(file) with yaml.safe_load(file). This is necessary for yaml 6.0 compatability, and also closes a possible code injection possiblity.

Fixes # 3100

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• [ ]

How Has This Been Tested?

Tests for the modbus_tk driver have been run manually, and work after the change.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules