nir: remove nir_strip stub declaration

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6328>
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index cbb5893..d538954 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -4678,8 +4678,6 @@
                                   nir_should_vectorize_mem_func callback,
                                   nir_variable_mode robust_modes);
 
-void nir_strip(nir_shader *shader);
-
 void nir_sweep(nir_shader *shader);
 
 void nir_remap_dual_slot_attributes(nir_shader *shader,