Doc: Error message: unexpected \new (3285) (issue 8581044)

[ianhulin44]

Maybe say "double angle brackets" for '<< ... >>' blocks, as simply
"angle brackets" implies '< ... >'


https://codereview.appspot.com/8581044/diff/1/Documentation/usage/running.itely
File Documentation/usage/running.itely (right):

https://codereview.appspot.com/8581044/diff/1/Documentation/usage/running.itely#newcode1056
Documentation/usage/running.itely:1056: @address@hidden @dots{} @}}, or angle
brackets, @code{<< @dots{} >>}, like
",or double angle brackets"

https://codereview.appspot.com/8581044/diff/1/Documentation/usage/running.itely#newcode1071
Documentation/usage/running.itely:1071: curly or angle brackets.
"curly or double angle brackets"

https://codereview.appspot.com/8581044/diff/1/Documentation/usage/running.itely#newcode1086
Documentation/usage/running.itely:1086: but more likely you should be
using angle brackets so the new staves
"but more likely you should be using double angle brackets so the new
staves"

https://codereview.appspot.com/8581044/