Android: Update docs to say Java 8 is required

docs/android_build_instructions.md

Index: docs/android_build_instructions.md
diff --git a/docs/android_build_instructions.md b/docs/android_build_instructions.md
index 2e2cf1bfd23fbab66113ef85f1a94205034ae54e..1b9044366fb4eea80eb27f924a3895d65d7be33f 100644
--- a/docs/android_build_instructions.md
+++ b/docs/android_build_instructions.md
@@ -112,19 +112,6 @@ keys](https://www.chromium.org/developers/how-tos/api-keys) if you want your
 build to talk to some Google services, but this is not necessary for most
 development and testing purposes.
 
-### Configure the JDK
-
-Make also sure that OpenJDK 1.7 is selected as default:

[jbudorick, 2017/01/31 21:51:35]

I think this section should still be there, just w/ 1.8 referenced instead of
1.7.

[agrieve, 2017/02/01 02:39:21]

We instruct devs to run build/install-build-deps-android.sh two steps above. So
long as the script checks for java8, I think it'd be more valuable to make our
docs shorter.

-
-```shell
-$ sudo update-alternatives --config javac
-$ sudo update-alternatives --config java
-$ sudo update-alternatives --config javaws
-$ sudo update-alternatives --config javap
-$ sudo update-alternatives --config jar
-$ sudo update-alternatives --config jarsigner
-```
-
 ## Setting up the build
 
 Chromium uses [Ninja](https://ninja-build.org) as its main build tool along