Fix #2317, Correct unbalanced brackets in `CFE_MSG_CMD_HDR_INIT` macro

[thnkslprpt]

Checklist

• [x] I reviewed the Contributing Guide.
• [x] I signed and emailed the appropriate Contributor License Agreement to [email protected] and copied [email protected].

Describe the contribution

• Fixes #2317
  • unbalanced brackets/parentheses corrected

Testing performed GitHub CI actions all passing successfully.

Expected behavior changes Balanced brackets - could avoid future compiler warnings/errors or code bugs if not picked up by the compiler.

Contributor Info Avi Weiss @thnkslprpt

[skliper]

Ouch. Slightly related:

• #1810

Recommend adding tests that use this in CI.