fix README after applied suggestion

Author: stokado

version-diff/README.md

@@ -13,6 +13,6 @@ Execute this command in a sample directory:
 * `1.6.8` and `2.2.2` are the versions of the Maven artifact to compare.
 * By default, the repository URL is https://repo.maven.apache.org/maven2/io/ktor.
   If you want to use a repository other than the default, provide it explicitly as the third argument:
-  ```bash
+```bash
 ./gradlew run --args="2.3.13 3.0.0 https://oss.sonatype.org/content/repositories/releases/io/ktor"
 ```