glsl-1.30: change offset for gl_ClipDistance test

With the offsets used to test gl_ClipDistance for the GL_LINES primitives, the test fails for Raspberry Pi 4 device because the rendered line is shifted 1 pixel to the left.

This is caused because the device uses 6 bits for subpixel precision in the line rasterizer, so the final line is displaced 1 pixel regarding test expects to be rendered.

Slighlty changing the offset makes the line to be rendered where we want, and it doesn't affect the purpose of the test, which is verifying that gl_ClilpDistance affects the primitive types correctly.