[spec] Fix typo in element execution (#1544)

Author: ia0

document/core/exec/modules.rst

@@ -729,8 +729,8 @@ where:
 .. math::
    \begin{array}{@{}l}
    \F{runelem}_i(\{\ETYPE~\X{et}, \EINIT~\reff^n, \EMODE~\EPASSIVE\}) \quad=\quad \epsilon \\
-   \F{runelem}_i(\{\ETYPE~\X{et}, \EINIT~\reff^n, \EMODE~\EACTIVE \{\ETABLE~0, \EOFFSET~\instr^\ast~\END\}\}) \quad=\\ \qquad
-     \instr^\ast~(\I32.\CONST~0)~(\I32.\CONST~n)~(\TABLEINIT~i)~(\ELEMDROP~i) \\
+   \F{runelem}_i(\{\ETYPE~\X{et}, \EINIT~\reff^n, \EMODE~\EACTIVE \{\ETABLE~x, \EOFFSET~\instr^\ast~\END\}\}) \quad=\\ \qquad
+     \instr^\ast~(\I32.\CONST~0)~(\I32.\CONST~n)~(\TABLEINIT~x~i)~(\ELEMDROP~i) \\
    \F{runelem}_i(\{\ETYPE~\X{et}, \EINIT~\reff^n, \EMODE~\EDECLARATIVE\}) \quad=\\ \qquad
      (\ELEMDROP~i) \\[1ex]
    \F{rundata}_i(\{\DINIT~b^n, \DMODE~\DPASSIVE\}) \quad=\quad \epsilon \\