Fix eu translations

Since reviewers could not agree on a way to cap group headers, simply omitting them altogether by default.
Test still reproduces the original issue when flag is set on:
… org.eclipse.jetty.server.HttpChannel$CommitCallback failed
WARNING: Commit failed
java.io.IOException: Response header too large
	at org.eclipse.jetty.http.HttpGenerator.generateResponse(HttpGenerator.java:402)
	at org.eclipse.jetty.server.HttpConnection$SendCallback.process(HttpConnection.java:655)
	at …
	at hudson.security.AccessDeniedHandlerImpl.handle(AccessDeniedHandlerImpl.java:57)
	at …
Caused by: java.nio.BufferOverflowException
	at java.nio.HeapByteBuffer.put(HeapByteBuffer.java:189)
	at java.nio.ByteBuffer.put(ByteBuffer.java:859)
	at org.eclipse.jetty.http.HttpGenerator.putTo(HttpGenerator.java:1087)
	at org.eclipse.jetty.http.HttpGenerator.generateHeaders(HttpGenerator.java:705)
	at org.eclipse.jetty.http.HttpGenerator.generateResponse(HttpGenerator.java:387)
	... 66 more
java.lang.AssertionError: expected:<403> but was:<500>
	at org.junit.Assert.fail(Assert.java:88)
	at org.junit.Assert.failNotEquals(Assert.java:834)
	at org.junit.Assert.assertEquals(Assert.java:645)
	at org.junit.Assert.assertEquals(Assert.java:631)
	at hudson.security.AccessDeniedException2Test.youAreInGroupHeaders(AccessDeniedException2Test.java:56)

[FIX JENKINS-26977] Use project-specific check URL

Polish translations

[JENKINS-41511] Don't try to set slaveAgentPort when it is enforced

[JENKINS-34065] Deleting obsolete pinning UI

Print stack trace in logical order

For some reason, Bulgarian translations included a gratuitous newline between key and value, which core/move-l10n.groovy does not yet grok.

This reverts commit 4c1a23d9.
No longer needed as of 2527e66d.