ensure doctests are not elided by linker

opts.set_disable_data_sync was removed from RocksDB (commit eb912a9),
but our doctest didn't fail because the function opts.set_disable_data_sync
was called in, badly_tuned_for_somebody_elses_disk, was elided by the linker.
Remove this function to ensure the doctest actually exercises the code
path.

src/lib.rs

@@ -119,8 +119,6 @@ pub struct BlockBasedOptions {
 /// use rocksdb::{Options, DB};
 /// use rocksdb::DBCompactionStyle;
 ///
-/// fn badly_tuned_for_somebody_elses_disk() -> DB {
-///    let path = "path/for/rocksdb/storageX";
 /// let mut opts = Options::default();
 /// opts.create_if_missing(true);
 /// opts.set_max_open_files(10000);
@@ -139,9 +137,6 @@ pub struct BlockBasedOptions {
 /// opts.set_max_background_compactions(4);
 /// opts.set_max_background_flushes(4);
 /// opts.set_disable_auto_compactions(true);
-///
-///    DB::open(&opts, path).unwrap()
-/// }
 /// ```
 pub struct Options {
     inner: *mut ffi::rocksdb_options_t,