revise document of installing ballista pinned to specified version (#2034)

Co-authored-by: duripeng <[email protected]>

Author: WinkerDu

ballista/rust/client/README.md

@@ -49,8 +49,8 @@ A simple way to start a local cluster for testing purposes is to use cargo to in
 the scheduler and executor crates.
 
 ```bash
-cargo install ballista-scheduler
-cargo install ballista-executor
+cargo install --locked ballista-scheduler
+cargo install --locked ballista-executor
 ```
 
 With these crates installed, it is now possible to start a scheduler process.

docs/source/user-guide/distributed/deployment/cargo-install.md

@@ -23,8 +23,8 @@ A simple way to start a local cluster for testing purposes is to use cargo to in
 the scheduler and executor crates.
 
 ```bash
-cargo install ballista-scheduler
-cargo install ballista-executor
+cargo install --locked ballista-scheduler
+cargo install --locked ballista-executor
 ```
 
 With these crates installed, it is now possible to start a scheduler process.