fix(st7789): Remove gamma configuration, relying on defaults

[finger563]

Description

• Remove initialization commands for setting initial values for gamma controls from ST7789 driver

Motivation and Context

Improves color reproduction on T Dongle S3

How has this been tested?

• Build and run esp-box/example
• Build and run t-deck/example
• Build and run t-dongle-s3/example

Screenshots (if appropriate, e.g. schematic, board, console logs, lab pictures):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update
• Hardware (schematic, board, system design) change
• Software change

Checklist:

• My change requires a change to the documentation.
• I have added / updated the documentation related to this change via either README or WIKI

Software

• I have added tests to cover my changes.
• I have updated the .github/workflows/build.yml file to add my new test to the automated cloud build github action.
• All new and existing tests passed.
• My code follows the code style of this project.