[lldb][NFC] Remove unused field Platform::m_remote_url (llvm#118411)

Related:
https://discourse.llvm.org/t/rfc-lldb-a-proposal-to-refactor-platform/82697

Author: bulbazord

lldb/include/lldb/Target/Platform.h

@@ -473,8 +473,6 @@ class Platform : public PluginInterface {
                       LLVM_PRETTY_FUNCTION, GetName()));
   }
 
-  const std::string &GetRemoteURL() const { return m_remote_url; }
-
   bool IsHost() const {
     return m_is_host; // Is this the default host platform?
   }
@@ -977,7 +975,6 @@ class Platform : public PluginInterface {
   std::string m_sdk_build;
   FileSpec m_working_dir; // The working directory which is used when installing
                           // modules that have no install path set
-  std::string m_remote_url;
   std::string m_hostname;
   llvm::VersionTuple m_os_version;
   ArchSpec