[effects/zoom] Set wrap mode for cursor texture

Summary:
With the Oxygen cursor theme, a visual glitch can appear in the
bottom-left corner of the cursor when the screen is zoomed in.

The reason for that is we're using GL_REPEAT for GL_TEXTURE_WRAP_S
and GL_TEXTURE_WRAP_T. So, when the linear filter samples neighboring
texels in the bottom, it can sample some texels from the top (because of
GL_REPEAT).

To fix that, we have to set the wrap mode to GL_CLAMP_TO_EDGE.

BUG: 338254
FIXED-IN: 5.14.0

Test Plan:
Before:
{F6303912}

After:
{F6303913}

Tried other cursor themes(Breeze and Adwaita), everything looks okay.

Reviewers: #kwin, davidedmundson

Reviewed By: #kwin, davidedmundson

Subscribers: davidedmundson, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D15949