Fix spelling in completion.go

Signed-off-by: knrt10 <tripathi.kautilya@gmail.com>

cmd/helm/completion.go

@@ -151,7 +151,7 @@ __helm_compgen() {
 	fi
 	for w in "${completions[@]}"; do
 		if [[ "${w}" = "$1"* ]]; then
-			# Use printf instead of echo beause it is possible that
+			# Use printf instead of echo because it is possible that
 			# the value to print is -n, which would be interpreted
 			# as a flag to echo
 			printf "%s\n" "${w}"