[network-manager-applet] Fix capitalization in one more recently added translatable string

[Piotr Drąg <piotrdrag src gnome org>]

commit a299560f6f79c7bf8167b52b9519b63c32f0b8bb
Author: Piotr Drąg <piotrdrag gmail com>
Date:   Fri Dec 16 16:27:41 2016 +0100

    Fix capitalization in one more recently added translatable string

 src/connection-editor/page-proxy.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/connection-editor/page-proxy.c b/src/connection-editor/page-proxy.c
index 45436e2..6d82cb3 100644
--- a/src/connection-editor/page-proxy.c
+++ b/src/connection-editor/page-proxy.c
@@ -216,7 +216,7 @@ ce_page_proxy_new (NMConnectionEditor *editor,
                                           "ProxyPage",
                                           _("Proxy")));
        if (!self) {
-               g_set_error_literal (error, NMA_ERROR, NMA_ERROR_GENERIC, _("Could not load Proxy user 
interface."));
+               g_set_error_literal (error, NMA_ERROR, NMA_ERROR_GENERIC, _("Could not load proxy user 
interface."));
                return NULL;
        }