markdown: Remove P tag that wraps the html

The Comrak lib that we're using wraps each parsed markdown with a
`<p>...</p>\n` so we need to remove to avoid the modification of the
real message.

See #210
1 job for master in 13 minutes and 54 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
failed #27828
flatpak

00:13:54

 
Name Stage Failure
failed
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running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

Creating cache flatpak...
.flatpak-builder/cache/: found 143 matching files
target/: found 8321 matching files
Created cache
ERROR: Job failed (system failure): Error response from daemon: devmapper: Thin Pool has 157048 free data blocks which is less than minimum required 163840 free data blocks. Create more free space in thin pool or use dm.min_free_space option to change behavior