Change connected() to take &self instead of &mut self

Signed-off-by: cuishuang <imcusg@gmail.com>

Author: cuishuang

src/remote.rs

@@ -225,7 +225,7 @@ impl<'repo> Remote<'repo> {
     }
 
     /// Check whether the remote is connected
-    pub fn connected(&mut self) -> bool {
+    pub fn connected(&self) -> bool {
         unsafe { raw::git_remote_connected(self.raw) == 1 }
     }
 
@@ -759,7 +759,7 @@ impl<'cb> Binding for PushOptions<'cb> {
 
 impl<'repo, 'connection, 'cb> RemoteConnection<'repo, 'connection, 'cb> {
     /// Check whether the remote is (still) connected
-    pub fn connected(&mut self) -> bool {
+    pub fn connected(&self) -> bool {
         self.remote.connected()
     }