plugins: make plugins shared modules again

This reverts the main part of commit 4a264252a7.

As plugins are the prime use case for `shared_module`
getting rid of the warning from meson about linking against shared modules
weighs less heavy.

plugins/sip/meson.build

@@ -64,11 +64,10 @@ sip_enums = gnome.mkenums('calls-sip-enums',
 
 sip_sources += sip_enums
 
-calls_sip = shared_library(
+calls_sip = shared_module(
   'sip',
   sip_sources, config_h,
   dependencies: sip_deps,
-  link_args: '-Wl,--unresolved-symbols=ignore-in-object-files',
   include_directories: src_include,
   install: true,
   install_dir: sip_install_dir