Core/VideoCommon: Fix duplicate OSD Custom Textures messages

[dreamsyntax]

Resolves duplicate OSD messages for Loading and Found custom textures.

Upon VideoBackend initialization HiresTexture::Init will be called, which previously called HiresTexture::Update.
This PR removes HiresTexture::Init as it no longer serves a purpose.

Before:

After:

Reproduce Steps:

1. Enable Graphics -> Advanced -> Load Custom Textures
2. (Optional) Enable Prefetch Custom Textures (this changes the message between Loading and Found)
3. Launch a game
4. Observe the double message

Suggested Testing:

1. Test with game window embedded in Main Window, and without
2. Test with DynamicInputTexture scenarios
3. Test with multi-layer texture scenarios (e.g. 'GUP' folder and 'GUPR8P' folder)
4. Launching a game from the Wii menu and make sure the textures load. - iwubcode

[iwubcode]

One other thing that probably needs to be tested: launching a game from the Wii menu and make sure the textures load..

[dreamsyntax]

It turns out 3x can occur for Wii menu:

The launching a game from wii menu failed to refresh textures, so I'll be swapping the removed call to keep the gameID change instead.

[dreamsyntax]

It turns out 3x can occur for Wii menu:

With the latest commit, now it is 2x. This is expected as the Title loaded changes twice within the Wii Menu on boot (before entering a game).

My own testing (linux):

• Test with game window embedded in Main Window, and without ✔️
• Test with multi-layer texture scenarios (e.g. 'GUP' folder and 'GUPR8P' folder) ✔️
• Launching a game from the Wii menu and make sure the textures load. - iwubcode ✔️

I have not tested:

• Test with DynamicInputTexture scenarios

[dreamsyntax]

Removing init seems to behave exactly the same; I would just need someone to OK the solution.