Update dependencies.md (#610)
The word 'Optional dependencies' is error, I changed 'Optinal' to 'Optional'
diff --git a/docs/en-us/user/dependencies.md b/docs/en-us/user/dependencies.md
index 437dce5..9a1a853 100644
--- a/docs/en-us/user/dependencies.md
+++ b/docs/en-us/user/dependencies.md
@@ -19,7 +19,7 @@
* spring-context.jar [^4]: If you are using `ServiceConfig` and `ReferenceConfig` API calls, is not required.
* netty.jar [^5]: if `<dubbo:protocol server="mina"/>` or `<dubbo:protocol server="grizzly"/>`，Then change to mina.jar or grizzly.jar. If `<protocol name="rmi"/>`， is not required.
-## Optinal dependencies
+## Optional dependencies
These dependencies needs to be added to project manually，when you need them.
* netty-all 4.0.35.Final
@@ -55,4 +55,4 @@
[^3]: Bytecode generation
[^4]: Configuration parsing
[^5]: Network transmission
-[^6]: JAVAEE
\ No newline at end of file
+[^6]: JAVAEE
