Test page: replace inverted section banners with plain '=' rules, frame page with '-'

Matches the style settled on for the print-issues receipt -- '=' for
labeled section breaks, '-' for the plain top/bottom frame, no more
fully blacked-out rows.

app.rb

@@ -132,8 +132,9 @@ helpers do
   def print_epson_test_page
     receipt = ReceiptBuilder.new
     receipt.align(:center).bold.size(:big).text("TM-T20II TEST\n").size(:normal).bold(false)
+    receipt.align(:left).text(('-' * 48) + "\n")
 
-    receipt.align(:left).section_separator('TEXT STYLES')
+    receipt.section_separator('TEXT STYLES')
     receipt.text("Normal text\n")
     receipt.bold.text("Bold text\n").bold(false)
     receipt.underline.text("Underlined text\n").underline(false)
@@ -150,8 +151,8 @@ helpers do
     receipt.section_separator('IMAGE')
     receipt.align(:center).image(64, 64, checkerboard_bitmap)
 
-    receipt.section_separator
-    receipt.align(:left).text("Printed: #{Time.now.strftime('%Y-%m-%d %H:%M:%S')}\n")
+    receipt.align(:left).text(('-' * 48) + "\n")
+    receipt.text("Printed: #{Time.now.strftime('%Y-%m-%d %H:%M:%S')}\n")
     receipt.feed(3).cut
     receipt.print!(PRINTER_DEVICE_EPSON)
   end