Use plural form for 0 in French (#760)

See https://github.com/Plume-org/Plume/issues/745

po/plume-front/fr.po

@@ -10,7 +10,7 @@ msgstr ""
 "MIME-Version: 1.0\n"
 "Content-Type: text/plain; charset=UTF-8\n"
 "Content-Transfer-Encoding: 8bit\n"
-"Plural-Forms: nplurals=2; plural=(n > 1);\n"
+"Plural-Forms: nplurals=2; plural=(n != 1);\n"
 "X-Crowdin-Project: plume\n"
 "X-Crowdin-Language: fr\n"
 "X-Crowdin-File: /master/po/plume-front/plume-front.pot\n"

po/plume/fr.po

@@ -10,7 +10,7 @@ msgstr ""
 "MIME-Version: 1.0\n"
 "Content-Type: text/plain; charset=UTF-8\n"
 "Content-Transfer-Encoding: 8bit\n"
-"Plural-Forms: nplurals=2; plural=(n > 1);\n"
+"Plural-Forms: nplurals=2; plural=(n != 1);\n"
 "X-Crowdin-Project: plume\n"
 "X-Crowdin-Language: fr\n"
 "X-Crowdin-File: /master/po/plume/plume.pot\n"