Downgrade restriction from DoNotUse to NoExternalUse

There's a failure with accmod using DoNotUse. So taking the
easy path here to move forward. This will already have the intended
effect: clarify that TimeUnit2 is not to be used anymore.

core/src/main/java/hudson/util/TimeUnit2.java

@@ -31,7 +31,7 @@ package hudson.util;
 
 import hudson.RestrictedSince;
 import org.kohsuke.accmod.Restricted;
-import org.kohsuke.accmod.restrictions.DoNotUse;
+import org.kohsuke.accmod.restrictions.NoExternalUse;
 
 import java.util.concurrent.TimeUnit;
 
@@ -72,7 +72,7 @@ import java.util.concurrent.TimeUnit;
  */
 @Deprecated
 @RestrictedSince("TODO")
-@Restricted(DoNotUse.class)
+@Restricted(NoExternalUse.class)
 public enum TimeUnit2 {
     NANOSECONDS {
         @Override public long toNanos(long d)   { return d; }

pom.xml

@@ -95,7 +95,7 @@ THE SOFTWARE.
     <findbugs-maven-plugin.version>3.0.4</findbugs-maven-plugin.version>
     <findbugs.failOnError>true</findbugs.failOnError>
     <test-annotations.version>1.2</test-annotations.version>
-    <access-modifier.version>1.12-PR6-SNAPSHOT</access-modifier.version>
+    <access-modifier.version>1.11</access-modifier.version>
     <access-modifier-annotation.version>${access-modifier.version}</access-modifier-annotation.version> <!-- differing only where needed for timestamped snapshots -->
     <access-modifier-checker.version>${access-modifier.version}</access-modifier-checker.version>