Deduplicate the field of RootfsPropagation

There are two RootfsPropagation fields, one is Linux.RootfsPropagation,
the other one is LinuxRuntime.RootfsPropagation. They are duplicated,
one of them should be removed.

The RootfsPropagation is definitely a runtime specific configuration,
so we remove the one of Linux.RootfsPropagation.

And the description of it is moved from config-linux.md to
runtime-config-linux.md.

Signed-off-by: Lai Jiangshan <[email protected]>

Author: laijs

config-linux.md

@@ -16,16 +16,6 @@ Valid values are the string after `CAP_` for capabilities defined in [the man pa
     ]
 ```
 
-## Rootfs Mount Propagation
-
-rootfsPropagation sets the rootfs's mount propagation.
-Its value is either slave, private, or shared.
-[The kernel doc](https://www.kernel.org/doc/Documentation/filesystems/sharedsubtree.txt) has more information about mount propagation.
-
-```json
-    "rootfsPropagation": "slave",
-```
-
 ## User namespace mappings
 
 ```json

config_linux.go

@@ -13,8 +13,6 @@ type LinuxSpec struct {
 type Linux struct {
 	// Capabilities are linux capabilities that are kept for the container.
 	Capabilities []string `json:"capabilities"`
-	// RootfsPropagation is the rootfs mount propagation mode for the container.
-	RootfsPropagation string `json:"rootfsPropagation"`
 }
 
 // User specifies linux specific user and group information for the container's

runtime-config-linux.md

@@ -194,3 +194,13 @@ The actions and operators are strings that match the definitions in seccomp.h fr
        ]
    }
 ```
+
+## Rootfs Mount Propagation
+
+rootfsPropagation sets the rootfs's mount propagation.
+Its value is either slave, private, or shared.
+[The kernel doc](https://www.kernel.org/doc/Documentation/filesystems/sharedsubtree.txt) has more information about mount propagation.
+
+```json
+    "rootfsPropagation": "slave",
+```