fix(create-prs-to-update-vcs-repositories): specify language for fenc…

…ed code block

Signed-off-by: Junya Sasaki <junya.sasaki@tier4.jp>

create-prs-to-update-vcs-repositories/README.md

@@ -63,7 +63,7 @@ None.
 
 - Monitors all vcs-imported repositories in the ```autoware.repos``` (if default) which have a version with regular expression pattern ```r'\b(?<![^\s])\d+\.\d+\.\d+(?![-\w.+])\b'``` (if default).
   - This pattern match/mismatches for the following examples:
-```
+```plaintext
         "0.0.1",                # match
         "0.1.0",                # match
         "1.0.0",                # match
@@ -86,14 +86,14 @@ None.
 - If there is a new version with pattern matched in the vcs-imported repositories, create a PR for each repository, respectively.
 - The valid/invalid version update cases are as follows:
   - Valid ones (PR must be created):
-```
+```plaintext
     0.0.1  =>  0.0.2
     1.1.1  =>  1.2.1
     2.4.3  =>  3.0.0
 ```
 
   - Invalid ones (PR is not created):
-```
+```plaintext
     main       =>  0.0.1
     v0.0.1     =>  0.0.2
     xxx-0.0.1  =>  0.0.9