Stop requiring full commit SHA to be provided to bot

Since we query the GitHub API for the commit to learn parents, the full
commit hash isn't necessary. It's possibly we'll need more error
handling later for invalid commits and so on but for now this should be
sufficient to make it much easier to invoke the bot.

site/src/server.rs

@@ -549,14 +549,6 @@ pub fn handle_github(request: github::Request, data: &InputData) -> ServerResult
     if let Some(captures) = BODY_TRY_COMMIT.captures(&body) {
         if let Some(commit) = captures.get(1).map(|c| c.as_str()) {
             let commit = commit.trim_start_matches("https://github.com/rust-lang/rust/commit/");
-            if commit.len() != 40 {
-                post_comment(
-                    &data.config,
-                    &request.issue,
-                    "Please provide the full 40 character commit hash.",
-                )?;
-                return Ok(github::Response);
-            }
             let client = reqwest::Client::new();
             let commit_response: github::Commit = client
                 .get(&format!(