Ignore schema files for src tarball generation

Change-Id: I1aeafbe35f7badb6c59eddf79de4e96229b66886
Reviewed-on: https://gerrit.libreoffice.org/28494Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>
Tested-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>

.gitattributes

@@ -2,3 +2,4 @@
 *.sdw binary
 *.svg binary
 *.jcs binary
+schema/*/* export-ignore