Remove external/Java.Interop submodule in preparation for in-tree merge

Author: jonathanpeppers

.gitmodules

@@ -10,10 +10,6 @@
     path = external/debugger-libs
     url = https://github.com/mono/debugger-libs
     branch = main
-[submodule "external/Java.Interop"]
-    path = external/Java.Interop
-    url = https://github.com/dotnet/java-interop
-    branch = main
 [submodule "external/libunwind"]
     path = external/libunwind
     url = https://github.com/libunwind/libunwind.git