Revert "Add docs_preprocessor crate to support Zed Docs" (#16880)

Temporarily revert #16700 to deal with this error:

`error: manifest path `../crates/docs_preprocessor/Cargo.toml` does not
exist` as it was causing the docs-preprocessor not to run, meaning
unexpanded templates were showing up in the public docs.

Reverts zed-industries/zed#16700

Release Notes:

- N/A

crates/docs_preprocessor/src/templates/action.rs

@@ -1,50 +0,0 @@
-use crate::PreprocessorContext;
-use regex::Regex;
-use std::collections::HashMap;
-
-use super::Template;
-
-pub struct ActionTemplate;
-
-impl ActionTemplate {
-    pub fn new() -> Self {
-        ActionTemplate
-    }
-}
-
-impl Template for ActionTemplate {
-    fn key(&self) -> &'static str {
-        "action"
-    }
-
-    fn regex(&self) -> Regex {
-        Regex::new(&format!(r"\{{#{}(.*?)\}}", self.key())).unwrap()
-    }
-
-    fn parse_args(&self, args: &str) -> HashMap<String, String> {
-        let mut map = HashMap::new();
-        map.insert("name".to_string(), args.trim().to_string());
-        map
-    }
-
-    fn render(&self, _context: &PreprocessorContext, args: &HashMap<String, String>) -> String {
-        let name = args.get("name").map(String::as_str).unwrap_or_default();
-
-        let formatted_name = name
-            .chars()
-            .enumerate()
-            .map(|(i, c)| {
-                if i > 0 && c.is_uppercase() {
-                    format!(" {}", c.to_lowercase())
-                } else {
-                    c.to_string()
-                }
-            })
-            .collect::<String>()
-            .trim()
-            .to_string()
-            .replace("::", ":");
-
-        format!("<code class=\"hljs\">{}</code>", formatted_name)
-    }
-}

crates/docs_preprocessor/src/templates/keybinding.rs

@@ -1,36 +0,0 @@
-use crate::PreprocessorContext;
-use regex::Regex;
-use std::collections::HashMap;
-
-use super::Template;
-
-pub struct KeybindingTemplate;
-
-impl KeybindingTemplate {
-    pub fn new() -> Self {
-        KeybindingTemplate
-    }
-}
-
-impl Template for KeybindingTemplate {
-    fn key(&self) -> &'static str {
-        "kb"
-    }
-
-    fn regex(&self) -> Regex {
-        Regex::new(&format!(r"\{{#{}(.*?)\}}", self.key())).unwrap()
-    }
-
-    fn parse_args(&self, args: &str) -> HashMap<String, String> {
-        let mut map = HashMap::new();
-        map.insert("action".to_string(), args.trim().to_string());
-        map
-    }
-
-    fn render(&self, context: &PreprocessorContext, args: &HashMap<String, String>) -> String {
-        let action = args.get("action").map(String::as_str).unwrap_or("");
-        let macos_binding = context.find_binding("macos", action).unwrap_or_default();
-        let linux_binding = context.find_binding("linux", action).unwrap_or_default();
-        format!("<kbd class=\"keybinding\">{macos_binding}|{linux_binding}</kbd>")
-    }
-}