[docs][rust test] Adjusting spacing so posix-terminal doesn't overflow. Currently page is overflowing, but three-spaces seems to be the standard for all others

Change-Id: I619b03d4e6251ddb71402c6b185db4275850eb4e
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/707824
Commit-Queue: Auto-Submit <[email protected]>
Fuchsia-Auto-Submit: Andrew Pollack <[email protected]>
Reviewed-by: David Koloski <[email protected]>

Author: andrewpollack

docs/development/build/rust_test_suite.md

@@ -124,7 +124,7 @@ environments.
 
    Then set any relevant breakpoints and run the test with:
 
-    ```posix-terminal
+   ```posix-terminal
     ( \
      source $DEV_ROOT/rust/fuchsia-env.sh && \
      $DEV_ROOT/rust/x.py \
@@ -137,9 +137,9 @@ environments.
        -L $DEV_ROOT/sdk/arch/{{ '<var>' }}x64|a64{{ '</var>' }}/sysroot/lib
        -L $DEV_ROOT/sdk/arch/{{ '<var>' }}x64|a64{{ '</var>' }}/lib" \
     )
-    ```
+   ```
 
-   and `zxdb` will catch any crashes and break at any breakpoints you define.
+   And `zxdb` will catch any crashes and break at any breakpoints you define.
    This command is the same as the one above with the additional
    `-C debuginfo=2 -C opt-level=0` flags for debugging.