Fix extension name for EGLImage colorspace support.

The correct extension string is EGL_EXT_image_gl_colorspace, not
EGL_KHR_image_gl_colorspace. Qualcomm driver exposes both variants.

Bug: 32147090
Test: Used the application OpenGL ES CapsViewer from Play Store to
verify that the extension EGL_EXT_image_gl_colorspace is present
on Pixel XL.
Change-Id: I2f5e053b7210ac896f5122a46932b41e4db87c3b