Remove @ validation from network settings

Was a PR to completely remove space and @ validation (#985), but I can see people easily pressing space without meaning to and not being able to see what is wrong.  If someone makes a good reason for it to be needed I will remove it, but for now just removing @ so people can do basic auth.

app/src/main/java/github/daneren2005/dsub/fragments/SettingsFragment.java

@@ -803,7 +803,7 @@ public boolean onPreferenceChange(Preference preference, Object value) {
 						try {
 							String url = (String) value;
 							new URL(url);
-							if (url.contains(" ") || url.contains("@")) {
+							if (url.contains(" ")) {
 								throw new Exception();
 							}
 						} catch (Exception x) {
@@ -824,7 +824,7 @@ public boolean onPreferenceChange(Preference preference, Object value) {
 							}
 
 							new URL(url);
-							if (url.contains(" ") || url.contains("@")) {
+							if (url.contains(" ")) {
 								throw new Exception();
 							}
 						} catch (Exception x) {