doc: fixed a typo in a code example for ngx.re.match.

Signed-off-by: Yichun Zhang (agentzh) <agentzh@gmail.com>

Author: moonming

README.markdown

@@ -5909,7 +5909,7 @@ The optional fourth argument, `ctx`, can be a Lua table holding an optional `pos
 
  local ctx = { pos = 2 }
  local m, err = ngx.re.match("1234, hello", "[0-9]+", "", ctx)
-      -- m[0] = "34"
+      -- m[0] = "234"
       -- ctx.pos == 5
 ```
 

doc/HttpLuaModule.wiki

@@ -4932,7 +4932,7 @@ The optional fourth argument, <code>ctx</code>, can be a Lua table holding an op
 <geshi lang="lua">
     local ctx = { pos = 2 }
     local m, err = ngx.re.match("1234, hello", "[0-9]+", "", ctx)
-         -- m[0] = "34"
+         -- m[0] = "234"
          -- ctx.pos == 5
 </geshi>