java.util.Locale deprecation warnings

[xuwei-k]

https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/Locale.html#%3Cinit%3E(java.lang.String,java.lang.String,java.lang.String)

[warn] -- Deprecation Warning: /home/runner/work/scalatra/scalatra/core/src/main/scala/org/scalatra/i18n/I18nSupport.scala:101:16 
[warn] 101 |            new Locale(langCountry.head, langCountry.last)
[warn]     |                ^^^^^^
[warn]     |constructor Locale in class Locale is deprecated since : see corresponding Javadoc for more information.
[warn] -- Deprecation Warning: /home/runner/work/scalatra/scalatra/core/src/main/scala/org/scalatra/i18n/I18nSupport.scala:103:16 
[warn] 103 |            new Locale(langCountry.head)
[warn]     |                ^^^^^^
[warn]     |constructor Locale in class Locale is deprecated since : see corresponding Javadoc for more information.
[warn] -- Deprecation Warning: /home/runner/work/scalatra/scalatra/core/src/main/scala/org/scalatra/i18n/I18nSupport.scala:128:8 
[warn] 128 |    new Locale(token.head, token.last)
[warn]     |        ^^^^^^
[warn]     |constructor Locale in class Locale is deprecated since : see corresponding Javadoc for more information.