Update telescope.txt

[aryanexe07]

Description

Clarifies the behavior of height in the center layout strategy.
The previous wording ("How tall to make Telescope's entire layout") was
misleading — in the center layout, height controls the results window
height, not the full layout. Setting it too high can shrink or obscure
the preview window.

Also reverts an incorrect edit to the horizontal layout section.

Fixes #3623

Type of change

• This change requires a documentation update

How Has This Been Tested?

N/A — documentation-only change, no code was modified.

Configuration:
N/A

Checklist:

• My code follows the style guidelines of this project (stylua)
• 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 (lua annotations)

[aryanexe07]

sorry, the checklist was failing, i will redo and probably change some code