Remove extern crate semver.

Author: xiongmao86

tests/ui/single_component_use_path.fixed

@@ -2,7 +2,6 @@
 // compile-flags: --edition 2018
 #![warn(clippy::single_component_use_path)]
 
-extern crate semver;
 
 
 fn main() {

tests/ui/single_component_use_path.rs

@@ -2,7 +2,6 @@
 // compile-flags: --edition 2018
 #![warn(clippy::single_component_use_path)]
 
-extern crate semver;
 use semver;
 
 fn main() {

tests/ui/single_component_use_path.stderr

@@ -1,15 +1,11 @@
-error[E0254]: the name `semver` is defined multiple times
-  --> $DIR/single_component_use_path.rs:6:5
+error[E0432]: unresolved import `semver`
+  --> $DIR/single_component_use_path.rs:5:5
    |
-LL | extern crate semver;
-   | -------------------- previous import of the extern crate `semver` here
 LL | use semver;
-   |     ^^^^^^ `semver` reimported here
-   |
-   = note: `semver` must be defined only once in the type namespace of this module
+   |     ^^^^^^ no `semver` external crate
 
 error: this import is redundant
-  --> $DIR/single_component_use_path.rs:6:1
+  --> $DIR/single_component_use_path.rs:5:1
    |
 LL | use semver;
    | ^^^^^^^^^^^ help: remove it entirely
@@ -18,4 +14,4 @@ LL | use semver;
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0254`.
+For more information about this error, try `rustc --explain E0432`.