Improve documentation of 'remote_src' in the file copy module. (#23946)

Now that remote-to-remote copies are supported in the copy module,
the module documentation has been updated to indicate this in the
synopsis and examples to make the capability obvious for someone
skimming the documentation.

lib/ansible/modules/files/copy.py

@@ -29,7 +29,8 @@ module: copy
 version_added: "historical"
 short_description: Copies files to remote locations.
 description:
-    - The C(copy) module copies a file on the local box to remote locations. Use the M(fetch) module to copy files from remote locations to the local box.
+    - The C(copy) module copies a file from the local or remote machine to a location on the remote machine.
+      Use the M(fetch) module to copy files from remote locations to the local box.
       If you need variable interpolation in copied files, use the M(template) module.
 options:
   src:
@@ -146,6 +147,12 @@ EXAMPLES = '''
     src: /mine/sudoers
     dest: /etc/sudoers
     validate: 'visudo -cf %s'
+
+# Copy a "sudoers" file on the remote machine for editing
+- copy:
+    remote_src: true
+    src: /etc/sudoers
+    dest: /etc/sudoers.edit
 '''
 
 RETURN = '''