Fix trivial memory leaks in the shell and sqldiff programs.

FossilOrigin-Name: 272793e5edc47e431be77d589718a001f2696869e3e15f1371a1890645a995a7
diff --git a/tool/sqldiff.c b/tool/sqldiff.c
index 85cae56..123d5b4 100644
--- a/tool/sqldiff.c
+++ b/tool/sqldiff.c
@@ -473,6 +473,7 @@
     fprintf(out, "%s;\n", sqlite3_column_text(pStmt,0));
   }
   sqlite3_finalize(pStmt);
+  sqlite3_free(zId);
 }