Use proper Common Components team for co-ownership

[lloeki]

@ekump tells me this should probably be @DataDog/apm-common-components-core

Originally posted by @lloeki in #38

[ekump]

@DataDog/libdatadog is too broad. It consists of people from all the product teams and serverless. @DataDog/apm-common-components-core is the platform team for libdatadog. I think common components core and the ruby guild make sense for co-ownership.