Drop running 1000 models in the CI (#1411)

With PR #1403 , we added to the matrix to run tests on 500 & 1000
models. Although the job for
500 models completes in under 15 mins, the job for 1000 models is taking
significantly longer ~40+ mins as can be seen here
https://github.com/astronomer/astronomer-cosmos/actions/runs/12400943145/job/34619249671.

I suggest we drop running 1000 models and later add it to the matrix to
conditionally run only when a certain label is added to the PR i.e. when
we would actually like to benchmark on specific PRs. I have created a
follow-up issue for this
#1410

related: #1410

.github/workflows/test.yml

@@ -354,7 +354,7 @@ jobs:
       matrix:
         python-version: ["3.11"]
         airflow-version: ["2.8"]
-        num-models: [1, 10, 50, 100, 500, 1000]
+        num-models: [1, 10, 50, 100, 500]
     services:
       postgres:
         image: postgres