meta: Drop ctx->API checks.

meta: Drop ctx->API checks.

API is always API_OPENGL_COMPAT (since commit 4e4a537ad55f61a25,
"meta: Push into desktop GL mode when doing meta operations."),
so most of these checks do nothing.

We could instead check save->API to only bother setting/restoring
relevant GL state, but I'm not sure saving a few _mesa_set_enable
calls is worth the complexity.  My understanding is the point of
the ctx->API guards was to avoid raising GL errors.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>