Correct another case of arch specific file in noarch package.

The problems were introduced but not verified in last stages of review
request, when attempting to silence some bogus rpmlint warnings.

sagemath.spec

@@ -74,7 +74,7 @@ Name:		sagemath
 Group:		Applications/Engineering
 Summary:	A free open-source mathematics software system
 Version:	5.8
-Release:	4%{?dist}
+Release:	5%{?dist}
 # The file ${SAGE_ROOT}/COPYING.txt is the upstream license breakdown file
 # Additionally, every $files section has a comment with the license name
 # before files with that license
@@ -1185,6 +1185,7 @@ fi
 %{SAGE_LOCAL}/include
 %{SAGE_LOCAL}/lib
 %{SAGE_LOCAL}/share
+%{SAGE_ROOT}/doc
 %{SAGE_ROOT}/share
 %dir %{SAGE_DEVEL}
 %dir %{SAGE_PYTHONPATH}
@@ -1252,7 +1253,6 @@ fi
 #------------------------------------------------------------------------
 %files		doc
 # GPLv2+
-%{SAGE_ROOT}/doc
 %{SAGE_DEVEL}/doc
 %dir %{SAGE_DOC}
 %{SAGE_DOC}/common