hyprpm: add missing include for libc++ after 1c530cbc66 (#10344)

hyprpm/src/helpers/Sys.cpp:24:24: error: implicit instantiation of undefined temp
late 'std::basic_ostringstream<char>'
   24 |     std::ostringstream oss;
      |                        ^
/usr/include/c++/v1/__fwd/sstream.h:27:28: note: template is declared here
   27 | class _LIBCPP_TEMPLATE_VIS basic_ostringstream;
      |                            ^

hyprpm/src/helpers/Sys.cpp

@@ -4,6 +4,7 @@
 
 #include <pwd.h>
 #include <unistd.h>
+#include <sstream>
 #include <print>
 #include <filesystem>
 #include <algorithm>