Remove outdated comment referencing IE9 rule limit

lms/static/sass/application-rtl.scss.mako

-## Note: This Sass infrastructure is repeated in application-extend1 and application-extend2, but needed in order to address an IE9 rule limit within CSS - http://blogs.msdn.com/b/ieinternals/archive/2011/05/14/10164546.aspx
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 // lms - css application architecture
 // ====================
 

lms/static/sass/application.scss.mako

-## Note: This Sass infrastructure is repeated in application-extend1 and application-extend2, but needed in order to address an IE9 rule limit within CSS - http://blogs.msdn.com/b/ieinternals/archive/2011/05/14/10164546.aspx
-
 // lms - css application architecture
 // ====================