Fix error handling in sampler.rs

We were calling unwrap_err when failing to create a PythonSpy
object in sampler.rs (on the result of sending the error on
a channel), when we should have been calling unwrap. Fix.

See #644

src/sampler.rs

@@ -56,7 +56,7 @@ impl Sampler {
                     spy
                 }
                 Err(e) => {
-                    initialized_tx.send(Err(e)).unwrap_err();
+                    initialized_tx.send(Err(e)).unwrap();
                     return;
                 }
             };
@@ -308,7 +308,7 @@ impl PythonSpyThread {
                 }
                 Err(e) => {
                     warn!("Failed to profile python from process {}: {}", pid, e);
-                    initialized_tx.send(Err(e)).unwrap_err();
+                    initialized_tx.send(Err(e)).unwrap();
                     return;
                 }
             };