Update doctests for Context changes

Due to the Context having many methods removed, the doctests were
failing.

Update the doctests to use alternative methods to accomplish the same.

Example:

Before:
```rust
context.say("hi");
```

After:
```rust
message.channel_id.say("hi")
```

1 files changed, 2 insertions, 2 deletions

diff --git a/src/utils/builder/edit_role.rs b/src/utils/builder/edit_role.rs
index 3410417..e9b86e9 100644
--- a/src/utils/builder/edit_role.rs
+++ b/src/utils/builder/edit_role.rs
@@ -19,8 +19,8 @@ use ::model::{Permissions, Role, permissions};
 /// Create a hoisted, mentionable role named "a test role":
 ///
 /// ```rust,ignore
-/// // assuming you are in a `context` and a `guild_id` has been bound
-/// let role = context.create_role(guild_id, |r| r
+/// // assuming a `channel_id` and `guild_id` has been bound
+/// let role = channel_id.create_role(guild_id, |r| r
 ///     .hoist(true)
 ///     .mentionable(true)
 ///     .name("a test role"));