Fix gateway docs remove redundant files (#5072)

docs/gateway/b2.md

@@ -4,14 +4,14 @@ Minio Gateway adds Amazon S3 compatibility to Backblaze B2 Cloud Storage.
 ## Run Minio Gateway for Backblaze B2 Cloud Storage
 Please follow this [guide](https://www.backblaze.com/b2/docs/quick_account.html) to create an account on backblaze.com to obtain your access credentisals for B2 Cloud storage.
 
-### Using Binary
-Please download the test binary for gateway B2 support https://data.minio.io:10000/minio-b2/linux-amd64/minio-b2
+### Using Docker
+```
+docker run -p 9000:9000 --name azure-s3 \
+ -e "MINIO_ACCESS_KEY=b2_accound_id" \
+ -e "MINIO_SECRET_KEY=b2_application_key" \
+ minio/minio:edge gateway b2
+```
 
-```
-export MINIO_ACCESS_KEY=b2_accound_id
-export MINIO_SECRET_KEY=b2_application_key
-minio gateway b2
-```
 ## Test using Minio Browser
 Minio Gateway comes with an embedded web based object browser. Point your web browser to http://127.0.0.1:9000 ensure your server has started successfully.
 
@@ -35,12 +35,15 @@ mc ls myb2
 
 ### Known limitations
 Gateway inherits the following B2 limitations:
+
 - No support for CopyObject S3 API (There are no equivalent APIs available on Backblaze B2).
 - No support for CopyObjectPart S3 API (There are no equivalent APIs available on Backblaze B2).
 - Only read-only bucket policy supported at bucket level, all other variations will return API Notimplemented error.
+- DeleteObject() might not delete the object right away on Backblaze B2, so you might see the object immediately after a Delete request.
 
 Other limitations:
-- Bucket notification APIs are not supported on Gateway.
+
+- Bucket notification APIs are not supported.
 
 ## Explore Further
 - [`mc` command-line interface](https://docs.minio.io/docs/minio-client-quickstart-guide)