Use external/mime-support's mime.types rather than libcore's copy.

Libcore was carrying a copy of mime.types that is now also present
in external/mime-support, and exposed through a filegroup in another
CL in this CL topic. Because external/mime-support's filegroup
carries the file in the root level rather than in the libcore/net/
subdirectory, this CL updates MimeMap.java accordingly.

libcore's mime.types and the associated README are now redundant,
so this CL drops them.

Bug: 135431432
Test: Checked that libcore's and external/mime-support's mime.types
      were exactly identical before this CL:
 diff {libcore/luni/src/main/java/libcore/net,external/mime-support}/mime.types

Test: atest CtsLibcoreTestCases:libcore.libcore.net.MimeMapTest

Change-Id: I632d2977f6588d92177cf059d3c048e07c38f341
diff --git a/JavaLibrary.bp b/JavaLibrary.bp
index 824626a..bc44e71 100644
--- a/JavaLibrary.bp
+++ b/JavaLibrary.bp
@@ -52,9 +52,7 @@
     ],
     path: "luni/src/main/java/",
     srcs: [
-        "luni/src/main/java/libcore/net/mime.types",
         "luni/src/main/java/libcore/net/android.mime.types",
-        "luni/src/main/java/libcore/net/mime.types.README",
         "luni/src/main/java/java/util/logging/logging.properties",
         "luni/src/main/java/java/security/security.properties",
     ],
@@ -74,6 +72,7 @@
 core_resources = [
     ":core-luni-resources",
     ":core-ojluni-resources",
+    ":debian.mime.types",
 ]
 
 // The source files that go into core-oj.