docs: revisions to ndk download intro
docs: revisions to ndk download intro

Change-Id: Ib1ba3d5f0e727a1246dc92161b72bcfff6f9d772

pranav01/platform_manifest,see4ri/lolili,xorware/android_build,xorware/android_build,Hybrid-Power/startsync,xorware/android_build,fallouttester/platform_manifest,hagar006/platform_manifest,knone1/platform_manifest,xorware/android_build,xorware/android_build,ND-3500/platform_manifest,RR-msm7x30/platform_manifest