Merge bitcoin#14495: build: Warn (don't fail!) on spelling errors

c32cf6a Add ignored word: mut (practicalswift)
4ae50da Revert "qa: Fix codespell error and have lint-spelling error instead of warn" (practicalswift)

Pull request description:

  Revert `codespell` policy change introduced in bitcoin#14179.

  Context: bitcoin#13954 (comment)

Tree-SHA512: 4606b19bb32cdd661f90b3778759818d3493e5ed1a4a2f95982f07eeb6b9c889bc8d53cde31706e0a3b9524c3d3a7378f1b769a60baeb0d00da4c68fd3068114

test/lint/lint-spelling.ignore-words.txt

@@ -1,6 +1,7 @@
 cas
 hights
 mor
+mut
 objext
 unselect
 useable