Typo fix in spec, just one spurious `{` removed.

Change-Id: I11c468d59fc69b901a5947d06f1798984c7040c7
Reviewed-on: https://dart-review.googlesource.com/c/84429
Reviewed-by: Erik Ernst <eernst@google.com>
diff --git a/docs/language/dartLangSpec.tex b/docs/language/dartLangSpec.tex
index 3973357..5f20586 100644
--- a/docs/language/dartLangSpec.tex
+++ b/docs/language/dartLangSpec.tex
@@ -5289,7 +5289,7 @@
 a constant invocation of a constructor of the \code{Symbol} class,
 or to an object implementing the built-in class \code{Type}
 which was originally obtained by evaluating a constant type literal
-(\ref{{dynamicTypeSystem}).
+(\ref{dynamicTypeSystem}).
 % Needs 'free': `const <int, Function(Function<X>(X))>{}` is OK, but
 % `X` is not free.
 It is a compile-time error if a type argument of a constant map literal