Remove java_home GYP variable from webrtc/build/common.gypi
Remove java_home GYP variable from webrtc/build/common.gypi

The java_home variable is no longer used since
https://codereview.webrtc.org/1652123002 so it can be removed.
This is also needed to make it possible to roll
https://codereview.webrtc.org/1610243002/ into Chromium.

TBR=perkj@webrtc.org
BUG=webrtc:5418
NOTRY=True

Review URL: https://codereview.webrtc.org/1685083002

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#11548}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: c6344aac47c5234adf1ab2676f0184f0468a47b8

jchavanton/webrtc,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,jchavanton/webrtc,Alkalyne/webrtctrunk,jchavanton/webrtc,jchavanton/webrtc,jchavanton/webrtc,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,jchavanton/webrtc,jchavanton/webrtc,Alkalyne/webrtctrunk