What is the purpose of the change

Fix typo CHARECTER -> CHARACTER.
I have searched in opened PR.
Fell free to close it if it has be included in other PRs or It is not expected to change.

Brief changelog

Only rename SPLIT_IPV4_CHARECTER &SPLIT_IPV6_CHARECTER
to SPLIT_IPV4_CHARACTER &SPLIT_IPV6_CHARACTER .

Verifying this change

These two private variables do not affect the other methods or classes except getRandomPort .
The current test case 'NetUtilsTest' is enough.

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