Fix doc for target_type.

Author: calmofthestorm

src/tag.rs

@@ -86,7 +86,7 @@ impl<'repo> Tag<'repo> {
         unsafe { Binding::from_raw(raw::git_tag_target_id(&*self.raw)) }
     }
 
-    /// Get the OID of the tagged object of a tag
+    /// Get the ObjectType of the tagged object of a tag
     pub fn target_type(&self) -> Option<ObjectType> {
         unsafe { ObjectType::from_raw(raw::git_tag_target_type(&*self.raw)) }
     }