Remove protoc build requirement info (#88)

Since the last
[release](https://github.com/atuinsh/atuin/releases/tag/v18.4.0) protoc
is not required anymore because protox is used.

Author: PythonGermany

src/content/docs/guide/installation.mdx

@@ -38,8 +38,6 @@ If you don't wish to use the installer, the manual installation steps are as fol
         ```shell
         cargo install atuin
         ```
-
-        Please note that this requires the protobuf compiler to be installed
     </TabItem>
     <TabItem label="Homebrew">
         ```shell