Remove surplus double quotes

Closes #1877

src/sds.c

@@ -43,7 +43,7 @@
  * The string is always null-termined (all the sds strings are, always) so
  * even if you create an sds string with:
  *
- * mystring = sdsnewlen("abc",3");
+ * mystring = sdsnewlen("abc",3);
  *
  * You can print the string with printf() as there is an implicit \0 at the
  * end of the string. However the string is binary safe and can contain