cmd: fix cli.Print usage in docstring

s/contents/text/g

Change-Id: I8452a18da2145e4307fb8a009527ad0ea9a08b0f
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/6080
Reviewed-by: Paul Jolly <paul@myitcv.org.uk>

cmd/cue/cmd/cmd.go

@@ -126,7 +126,7 @@ the second to standard output (i.e. it echos it again).
 
 		// also starts after echo
 		print: cli.Print & {
-			contents: echo.stdout
+			text: echo.stdout
 		}
 	}
 

cmd/cue/cmd/help.go

@@ -407,7 +407,7 @@ the second to standard output (i.e. it echos it again).
 
 		// also starts after echo
 		print: cli.Print & {
-			contents: echo.stdout
+			text: echo.stdout
 		}
 	}
 

cmd/cue/cmd/testdata/script/help_cmd.txt

@@ -123,7 +123,7 @@ the second to standard output (i.e. it echos it again).
 
 		// also starts after echo
 		print: cli.Print & {
-			contents: echo.stdout
+			text: echo.stdout
 		}
 	}