[libc] Fix missing ; in spec.td. (#71977)

Author: lntue

libc/spec/spec.td

@@ -51,7 +51,7 @@ def LongDoubleType : NamedType<"long double">;
 def CharType : NamedType<"char">;
 
 // TODO: Add compatibility layer to use C23 type _Float128 if possible.
-def Float128Type : NamedType<"__float128">
+def Float128Type : NamedType<"__float128">;
 
 // Common types
 def VoidPtr : PtrType<VoidType>;