Update env variables warning languge

[amirbey]

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User Story

When adding environment variables, a Pages user should not be advised that the system is FISMA low

Background (Optional)

Pages will be FISMA moderate.

Acceptance Criteria

• [ ] Reword message to take into account that Pages is a FISMA Moderate system
• [ ] Change made live via deploy of Federalist

After evaluating, edit this part:

Level of effort - <low/medium/high>

Implementation outline (if higher than "low" effort):

• [ ] <TODO>