docs: fix typo (#137)

Author: vegetablest

docs/source/operators/deploy-docker.md

@@ -216,7 +216,7 @@ To see all configurable class-options for some <cmd>, use:
 Examples
 --------
 
-    jupyter-docker-spec install --language=R --kernel-name=r_docker --image_name=foo/my_r_kernel_image:v4_0
+    jupyter-docker-spec install --language=R --kernel-name=r_docker --image-name=foo/my_r_kernel_image:v4_0
 
     jupyter-docker-spec install --swarm --kernel-name=python_swarm
 

gateway_provisioners/cli/docker_specapp.py

@@ -37,7 +37,7 @@ class DockerSpecInstaller(BaseSpecApp):
     # Note that the left justification of the second example is necessary to ensure proper
     # alignment with the first example during --help output.
     examples = """
-    jupyter-docker-spec install --language=R --kernel-name=r_docker --image_name=foo/my_r_kernel_image:v4_0
+    jupyter-docker-spec install --language=R --kernel-name=r_docker --image-name=foo/my_r_kernel_image:v4_0
 
 jupyter-docker-spec install --swarm --kernel-name=python_swarm
     """