non-varargs call of varargs method with inexact argument type for last parameter in test code

### Affected version

HEAD

### Bug description

Should be straight-forward to clear these warnings

```
[WARNING] /Users/elharo/maven-shared-utils/src/test/java/org/apache/maven/shared/utils/StringUtilsTest.java:[564,55] non-varargs call of varargs method with inexact argument type for last parameter;
cast to java.lang.String for a varargs call
cast to java.lang.String[] for a non-varargs call and to suppress this warning
[WARNING] /Users/elharo/maven-shared-utils/src/test/java/org/apache/maven/shared/utils/StringUtilsTest.java:[566,58] non-varargs call of varargs method with inexact argument type for last parameter;
cast to java.lang.String for a varargs call
cast to java.lang.String[] for a non-varargs call and to suppress this warning
[WARNING] /Users/elharo/maven-shared-utils/src/test/java/org/apache/maven/shared/utils/StringUtilsTest.java:[804,59] non-varargs call of varargs method with inexact argument type for last parameter;
cast to java.lang.String for a varargs call
cast to java.lang.String[] for a non-varargs call and to suppress this warning
[WARNING] /Users/elharo/maven-shared-utils/src/test/java/org/apache/maven/shared/utils/StringUtilsTest.java:[806,62] non-varargs call of varargs method with inexact argument type for last parameter;
cast to java.lang.String for a varargs call
cast to java.lang.String[] for a non-varargs call and to suppress this warning
[WARNING] /Users/elharo/maven-shared-utils/src/test/java/org/apache/maven/shared/utils/StringUtilsTest.java:[1373,41] non-varargs call of varargs method with inexact argument type for last parameter;
```

Start in src/test/java/org/apache/maven/shared/utils/StringUtilsTest.java at lines 564, 566, 804, 806, and 1373, then inspect the varargs calls identified by the compiler warnings. Run the test suite or Maven build to confirm the warnings are gone and the StringUtils tests still pass.

Written by the indexing model from the issue text.