pkgconfig: do not add valgrind as requirement

For the same reasons commit 7aa28456d ("Add dependency type for
Valgrind") removed linking with valgrind, pkgconfig shouldn't generate
"Requirements" for it, in general.

This solves dbus meson port question/issue from:
https://gitlab.freedesktop.org/dbus/dbus/-/merge_requests/303#note_1444819

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

mesonbuild/modules/pkgconfig.py

@@ -116,6 +116,8 @@ class DependenciesHelper:
             if hasattr(obj, 'generated_pc'):
                 self._check_generated_pc_deprecation(obj)
                 processed_reqs.append(obj.generated_pc)
+            elif isinstance(obj, dependencies.ValgrindDependency):
+                pass
             elif isinstance(obj, dependencies.PkgConfigDependency):
                 if obj.found():
                     processed_reqs.append(obj.name)