chore: fix gitignore for cagent validation log

Signed-off-by: David Karlsson <35727626+dvdksn@users.noreply.github.com>

Author: dvdksn

.gitignore

@@ -15,4 +15,4 @@ cagent
 # cagent tmp files
 .cagent
 .upstream-issues.md
-.validation-log.md
+.validation.log