gitlint: screen multiple change-ids

Tested:
```
$ ./scripts/format-code.sh --enable commit_gitlint
Formatting code under .../openbmc-build-scripts
Running commit_gitlint
-: UC2 Multiple Chan

gitlint: screen multiple change-ids

Tested:
```
$ ./scripts/format-code.sh --enable commit_gitlint
Formatting code under .../openbmc-build-scripts
Running commit_gitlint
-: UC2 Multiple Change-Ids found in commit message body: "['Change-Id: Iec3501f75927d58bfe176423ce3eac824a0553d9', 'Change-Id: Iec3501f75927d58bfe176423ce3eac824a0553d9']"
commit_gitlint: FAILED
```

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Iec3501f75927d58bfe176423ce3eac824a0553d9

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