fix typos in share/scripts directory

Found via `codespell -q 3 -S "*.pdf,*.po,./.git,*.tosc,./waf,./share/patchfiles,./libs,./msvc_extra_headers,./share/web_surfaces,*.patch" -L acount,addin,ane,ba,buss,busses,caf,capela,devine,disconnectin,discreet,doubleclick,envolution,filetest,fo,ghandi,homs,hsi,layed,maschine,mis,nd,ontop,pass-thru,removeable,retrn,ro,scrollin,sectionin,seh,siz,sord,sur,te,trough,ue,wth`

share/scripts/trigger_mixer_scene.lua

@@ -3,7 +3,7 @@ ardour {
 	name        = "Mixer Scene Sequencer",
 	license     = "MIT",
 	author      = "John Devlin, Robin Gareus",
-	description = [[Recall a Mixer Scene when the playhead passes over a Marker named 'MS <nuber>' where <number> indicates the scene to recall.]]
+	description = [[Recall a Mixer Scene when the playhead passes over a Marker named 'MS <number>' where <number> indicates the scene to recall.]]
 }
 
 function factory ()