[Examples] change texture2d to texture

[CrackedPixel]

Texture2D is just an alias for Texture and i think it looks cleaner with just "Texture". It also makes it clear that there is NOT a Texture3D, etc

This pattern is also used in existing examples such as

raylib/examples/shaders/shaders_simple_mask.c

Line 67 in 97c02b2

Texture texDiffuse = LoadTexture("resources/plasma.png");

[raysan5]

@CrackedPixel As mentioned, I prefer not to change that naming.