Fix README

content/blog/2020/06/2020-06-17--opsv.md

@@ -33,7 +33,7 @@ Let's say I, Yarmo, would really like the world to know that I like pineapple. U
 
 The signed statement:
 
-```plaintext
+```text
 -----BEGIN PGP SIGNED MESSAGE-----
 Hash: SHA256
 
@@ -82,7 +82,7 @@ Remove the contents from the "Public Key (3: HKP)" field. It again verifies BUT
 
 The signature below does not contain a `userId`:
 
-```plaintext
+```text
 -----BEGIN PGP SIGNED MESSAGE-----
 Hash: SHA256
 
@@ -116,7 +116,7 @@ One could not sign a statement with my private key: I, and only I, have access t
 
 One could however simply take any of my signed messages and change the content. Like so:
 
-```plaintext
+```text
 -----BEGIN PGP SIGNED MESSAGE-----
 Hash: SHA256