ci: reduce e2e-cpu parallelization
If parallelization is too high, some test runners fail due to not
actually having any tests to run.
@@ -1239,7 +1239,7 @@ workflows:
- build-go
matrix:
parameters:
- parallelism: [8]
+ parallelism: [6]
tf1: [true]
mark: ["e2e_cpu"]
