pidgin/pidgin

Drop PidginCredentialProviderStore.

2021-05-13, Elliott Sales de Andrade
17208bd7a906
Drop PidginCredentialProviderStore.

It's no longer needed now that the prefs use a `GtkListBox`.

Testing Done:
Compile only.

Reviewed at https://reviews.imfreedom.org/r/650/
pidgin3_xml = configure_file(
input : 'pidgin3.xml.in',
output : 'pidgin3.xml',
configuration : version_conf,
install : true,
install_dir : get_option('datadir') / 'glade/catalogs')