Android: drop const from AndroidConfigurations::currentConfig()

Since the config can be expected to modify configuration values
(e.g. setEmulatorArgs()) it shouldn't be const, but can be set
to const whenever creating a reference that is not meant for
modifying the config.

Change-Id: I8c816a5422d4d57afa158c723d908e3a9a9a0db8
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/plugins/android/androidconfigurations.cpp

@@ -1408,7 +1408,7 @@ Environment AndroidConfigurations::toolsEnvironment(const AndroidConfig &config)
     return env;
 }
 
-const AndroidConfig &AndroidConfigurations::currentConfig()
+AndroidConfig &AndroidConfigurations::currentConfig()
 {
     return m_instance->m_config; // ensure that m_instance is initialized
 }