add go:1.15 kind to apiv1swagger (#4997)

Missing part of #4987 which added the go:1.15 kind.

Author: dgrove-oss

core/controller/src/main/resources/apiv1swagger.json

@@ -2009,6 +2009,7 @@
             "ruby:2.5",
             "ruby:default",
             "go:1.11",
+            "go:1.15",
             "go:default",
             "sequence",
             "swift:4.2",