misc. global typo fixes

Found with `codespell -q 3 -I ../pitivi--whitelist.txt --skip="*.po,*.svg"`
4 jobs for master in 76 minutes and 6 seconds (queued for 1 second)
Status Job ID Name Coverage
  Docker Image
passed #96314
pitivi:1.0

00:44:12

passed #96313
pitivi:master

01:01:35

 
  Build
passed #96315
build

00:11:36

 
  Test Results
passed #96316
test-results

00:02:55