lint can no longer properly detect unset Summary/Description

Since the Summary/Description can now be set in the app's source code, or
in fdroiddata/metadata/<packageName>/<locale>/*.txt, this lint check is
no longer valid.  It is important to check whether these texts are empty,
but it'll require some thinking about how and where to best to that.
`fdroid update` will have access to all that data, but perhaps at that
point it is too late.

Also, the current text prioritization puts Summary/Description in the
.txt/.yml file at the highest priority, overriding every other copy,
including in fdroiddata/metadata/<packageName>/<locale> and in the app's
source code.

fdroidserver/lint.py

@@ -88,8 +88,6 @@ regex_checks = {
          "Unnecessary trailing space"),
     ],
     'Summary': [
-        (re.compile(r'^$'),
-         "Summary yet to be filled"),
         (re.compile(r'.*\b(free software|open source)\b.*', re.IGNORECASE),
          "No need to specify that the app is Free Software"),
         (re.compile(r'.*((your|for).*android|android.*(app|device|client|port|version))', re.IGNORECASE),
@@ -102,8 +100,6 @@ regex_checks = {
          "Unnecessary trailing space"),
     ],
     'Description': [
-        (re.compile(r'^No description available$'),
-         "Description yet to be filled"),
         (re.compile(r'\s*[*#][^ .]'),
          "Invalid bulleted list"),
         (re.compile(r'^\s'),