gitlint: Fix dependabot exception

Match the full dependabot author name and ignore all (including user)
rules.

Signed-off-by: Pieter De Gendt <pieter.degendt@basalte.be>

.gitlint

@@ -61,5 +61,5 @@ ignore-merge-commits=false
 #files=gitlint/rules.py,README.md
 
 [ignore-by-author-name]
-regex=dependabot
+regex=^dependabot\[bot\]$
-ignore=body-requires-signed-off-by, max-line-length-with-exceptions
+ignore=all