fix BusyBox sed (#6327)

BusyBox sed works the same way as GNU sed

Signed-off-by: tipok <me@tipok.pro>

cmd/helm/completion.go

@@ -194,7 +194,7 @@ autoload -U +X bashcompinit && bashcompinit
 # use word boundary patterns for BSD or GNU sed
 LWORD='[[:<:]]'
 RWORD='[[:>:]]'
-if sed --help 2>&1 | grep -q GNU; then
+if sed --help 2>&1 | grep -q 'GNU\|BusyBox'; then
 	LWORD='\<'
 	RWORD='\>'
 fi