Update max environment query limit to 30

What does this MR do and why?

For #388952 (closed)

Based on this recommendation, we can update the environment query limit to 30.

For variables, the 90th Percentile of projects and namespaces will use anywhere between 10 - 25 variables. For environments, I believe that loading at least 30 environments (since the 90th Percentile of projects with 503 environments will use 29 environments) will help reduce the number of 503 errors that occur.

The changes are applicable under the ci_limit_environment_scope feature flag.

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