Fix capabilities plugin on kernels before 6.3

kernel_cap_t only handles the 6.3+ layout and raised for everything else.
Before 6.3 the same name exists as a typedef of kernel_cap_struct, whose
implementation already decodes the two-element cap array, so fall back to
it instead of raising.

volatility3/framework/symbols/linux/extensions/__init__.py

@@ -2375,9 +2375,8 @@ class kernel_cap_t(kernel_cap_struct):
             # In kernels >= 6.3 kernel_cap_t::val is a u64
             cap_value = self.val
         else:
-            raise exceptions.VolatilityException(
-                "Unsupported kernel capabilities implementation"
-            )
+            # Before 6.3 kernel_cap_t is a typedef of kernel_cap_struct
+            return super().get_capabilities()
 
         return cap_value & self.get_kernel_cap_full()