LibCore: Trim trailing whitespaces from ConfigFile values

Previously, trailing whitespaces were not removed from values in
config files. This could cause errors with poorly formatted files.
This commit fixes this by trimming whitespaces from values in
ConfigFile::reparse().

Userland/Libraries/LibCore/ConfigFile.cpp

@@ -106,7 +106,8 @@ void ConfigFile::reparse()
                 // We're not in a group yet, create one with the name ""...
                 current_group = &m_groups.ensure("");
             }
-            current_group->set(key_builder.to_string(), value_builder.to_string());
+            auto value_string = value_builder.to_string();
+            current_group->set(key_builder.to_string(), value_string.trim_whitespace(TrimMode::Right));
         }
         }
     }