Android: Remove min_sdk_version in GN (reland)

Android lint is changing, so min_sdk_version is no longer needed in GN.

Relanding because webrtc was able to roll chromium.

Bug: chromium:1017190
Change-Id: I3e351381cb735d511da648d4ef41613c923d62c7
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/174983
Commit-Queue: Peter Wen <wnwen@chromium.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31244}

webrtc.gni

@@ -992,14 +992,6 @@ if (is_android) {
       # Treat warnings as errors.
       errorprone_args += [ "-Werror" ]
 
-      # WebRTC supports API level 16 while Chromium only supports 19.
-      # (the manifest defines minimum supported SDK version)
-      if (defined(invoker.min_sdk_version)) {
-        min_sdk_version = invoker.min_sdk_version
-      } else {
-        min_sdk_version = 16
-      }
-
       # Add any arguments defined by the invoker.
       if (defined(invoker.errorprone_args)) {
         errorprone_args += invoker.errorprone_args