README.md: Fix MD014 warnings

The following warnings are generated by using markdownlint analysis:
```
MD014/commands-show-output Dollar signs used before commands without showing output [Context: "$ meson setup ... -Dlibpldm:ab..."]
```
Refer to markdown-lint [1] to fix MD014
[1]: https://github.com/updownpress/markdown-lint/blob/master/rules/014-commands-show-output.md

Signed-off-by: George Liu <liuxiwei@ieisystem.com>
Change-Id: Ib65ad072e91e49f7b04efcabe129c83b2c0b0edb
diff --git a/README.md b/README.md
index 874ad22..3424e9c 100644
--- a/README.md
+++ b/README.md
@@ -177,7 +177,7 @@
 subproject configuration syntax:
 
 ```shell
-$ meson setup ... -Dlibpldm:abi=deprecated,stable,testing ...
+meson setup ... -Dlibpldm:abi=deprecated,stable,testing ...
 ```
 
 ## OEM/vendor-specific functions