md2html: the default of stdin works fine

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

filters/html-converters/md2html

@@ -1,6 +1,5 @@
 #!/usr/bin/env python
 import markdown
-import sys
 print('''
 <style>
 .markdown-body {
@@ -282,5 +281,5 @@ print('''
 ''')
 print("<div class='markdown-body'>")
 # Note: you may want to run this through bleach for sanitization
-markdown.markdownFromFile(input=sys.stdin, output_format="html5")
+markdown.markdownFromFile(output_format="html5")
 print("</div>")