[spec] Remove obsolete note (#2071)

Author: zsakowitz

document/core/text/modules.rst

@@ -266,10 +266,6 @@ The data is written as a :ref:`string <text-string>`, which may be split up into
 
 $${grammar: Tdata_ Tdatastring {Tmemuse_/plain Toffset_/plain}}
 
-.. note::
-   In the current version of WebAssembly, the only valid memory index is 0
-   or a symbolic :ref:`memory identifier <text-id>` resolving to the same value.
-
 
 Abbreviations
 .............