tests/test_readers.py: Remove redundant 'expected' check in AdReaderTest
tests/test_readers.py: Remove redundant 'expected' check in AdReaderTest

AdReaderTest.test_article_with_asc_extension() has had duplicate
checks on the expected metadata since it was created by 49f481e3 (Add
asciidoc reader support, 2013-10-28).  This commit removes the
duplicate entry.

Scheirle/pelican,simonjj/pelican,catdog2/pelican,btnpushnmunky/pelican,0xMF/pelican,Summonee/pelican,gymglish/pelican,farseerfc/pelican,Rogdham/pelican,getpelican/pelican,deved69/pelican-1,getpelican/pelican,sunzhongwei/pelican,iKevinY/pelican,GiovanniMoretti/pelican,simonjj/pelican,zackw/pelican,HyperGroups/pelican,jvehent/pelican,catdog2/pelican,Summonee/pelican,JeremyMorgan/pelican,sunzhongwei/pelican,alexras/pelican,Rogdham/pelican,talha131/pelican,karlcow/pelican,fbs/pelican,liyonghelpme/myBlog,joetboole/pelican,lazycoder-ru/pelican,TC01/pelican,deved69/pelican-1,ls2uper/pelican,51itclub/pelican,garbas/pelican,UdeskDeveloper/pelican,koobs/pelican,janaurka/git-debug-presentiation,jo-tham/pelican,treyhunner/pelican,ingwinlu/pelican,TC01/pelican,ehashman/pelican,51itclub/pelican,UdeskDeveloper/pelican,kernc/pelican,koobs/pelican,douglaskastle/pelican,alexras/pelican,ehashman/pelican,jimperio/pelican,florianjacob/pelican,UdeskDeveloper/pelican,Summonee/pelican,liyonghelpme/myBlog,crmackay/pelican,arty-name/pelican,iurisilvio/pelican,51itclub/pelican,btnpushnmunky/pelican,treyhunner/pelican,avaris/pelican,liyonghelpme/myBlog,iurisilvio/pelican,koobs/pelican,abrahamvarricatt/pelican,crmackay/pelican,btnpushnmunky/pelican,treyhunner/pelican,number5/pelican,jimperio/pelican,eevee/pelican,Polyconseil/pelican,kennethlyn/pelican,11craft/pelican,11craft/pelican,iKevinY/pelican,abrahamvarricatt/pelican,11craft/pelican,Polyconseil/pelican,Rogdham/pelican,lazycoder-ru/pelican,talha131/pelican,ehashman/pelican,deved69/pelican-1,lazycoder-ru/pelican,Scheirle/pelican,GiovanniMoretti/pelican,eevee/pelican,HyperGroups/pelican,goerz/pelican,joetboole/pelican,catdog2/pelican,kernc/pelican,jimperio/pelican,sunzhongwei/pelican,goerz/pelican,abrahamvarricatt/pelican,deanishe/pelican,joetboole/pelican,garbas/pelican,janaurka/git-debug-presentiation,deanishe/pelican,liyonghelpme/myBlog,farseerfc/pelican,deanishe/pelican,rbarraud/pelican,HyperGroups/pelican,iurisilvio/pelican,sunzhongwei/pelican,number5/pelican,levanhien8/pelican,gymglish/pelican,lucasplus/pelican,JeremyMorgan/pelican,liyonghelpme/myBlog,TC01/pelican,JeremyMorgan/pelican,douglaskastle/pelican,douglaskastle/pelican,zackw/pelican,rbarraud/pelican,rbarraud/pelican,Scheirle/pelican,ls2uper/pelican,levanhien8/pelican,GiovanniMoretti/pelican,kennethlyn/pelican,kernc/pelican,justinmayer/pelican,crmackay/pelican,karlcow/pelican,gymglish/pelican,goerz/pelican,florianjacob/pelican,zackw/pelican,jo-tham/pelican,eevee/pelican,lucasplus/pelican,number5/pelican,ls2uper/pelican,levanhien8/pelican,simonjj/pelican,karlcow/pelican,alexras/pelican,lucasplus/pelican,florianjacob/pelican,garbas/pelican,janaurka/git-debug-presentiation,ingwinlu/pelican,jvehent/pelican,jvehent/pelican,avaris/pelican,kennethlyn/pelican,ionelmc/pelican