Fix typos in README.

[ghuls]

Fix typos in README.

Change:

Thanks to Apoorv Sharma @apoorv-sharma, hnswlib now supports true element updates (the interface remained the same, but when you the perfromance/memory should not degrade as you update the element embeddinds).

Thanks to Dmitry @2ooom, hnswlib got a boost in performance for vector dimensions that are not mutiple of 4

To:

Thanks to Apoorv Sharma @apoorv-sharma, hnswlib now supports true element updates (the interface remained the same, but when you the performance/memory should not degrade as you update the element embeddings).

Thanks to Dmitry @2ooom, hnswlib got a boost in performance for vector dimensions that are not multiple of 4.

[yurymalkov]

@ghuls thanks for reporting. Those typos are already fixed in develop branch (#253 )