Simplify the name import-versions to versions.

Import is implied as this is the child of the import clause.

yang-semver/draft-verdt-netmod-yang-semver.xml

@@ -662,7 +662,7 @@
     </t>
   </list>
   The patch modifier letter is not included as part of the
-  'semver:import-version' argument, and is entirely ignored for import
+  'semver:versions' argument, and is entirely ignored for import
   statement module version number comparisons.
   </t>
   <section title="Module import examples">
@@ -678,7 +678,7 @@
       <figure>
         <artwork>
 import example-module {
-  semver:import-versions 1.1.2;
+  semver:versions 1.1.2;
 }
        </artwork>
       </figure>
@@ -692,7 +692,7 @@ import example-module {
       <figure>
         <artwork>
 import example-module {
-  semver:import-versions 1.2.0+;
+  semver:versions 1.2.0+;
 }
         </artwork>
       </figure>
@@ -707,9 +707,9 @@ import example-module {
       <figure>
         <artwork>
 import example-module {
-  semver:import-versions 1.1.0-1.1.1;
-  semver:import-versions 1.2.0;
-  semver:import-versions 1.3.0+;
+  semver:versions 1.1.0-1.1.1;
+  semver:versions 1.2.0;
+  semver:versions 1.3.0+;
 }
         </artwork>
       </figure>
@@ -723,7 +723,7 @@ import example-module {
       <figure>
         <artwork>
 import example-module {
-  semver:import-versions 1.0.0-1.MAX.MAX;
+  semver:versions 1.0.0-1.MAX.MAX;
 }
         </artwork>
       </figure>
@@ -1166,7 +1166,7 @@ module ietf-semver {
        YANG Semantic Versioning for Modules";
   }
 
-  extension import-versions {
+  extension versions {
     argument version-clause;
     description
       "This extension specifies an acceptable set of semantic