doc: update AIX to GCC8 for v16.x

PR-URL: #37677 Refs: nodejs/build#2445 Reviewed-By: Stewart X Addison <sxa@redhat.com> Reviewed-By: Michael Dawson <midawson@redhat.com> Reviewed-By: Richard Lau <rlau@redhat.com> Reviewed-By: Beth Griggs <bgriggs@redhat.com> Reviewed-By: Rich Trott <rtrott@gmail.com>

Author: Ash Cripps

BUILDING.md

@@ -116,7 +116,7 @@ platforms. This is true regardless of entries in the table below.
 | macOS | x64 | >= 10.13 | Tier 1 | |
 | macOS | arm64 | >= 11 | Experimental | |
 | SmartOS | x64 | >= 18 | Tier 2 | |
-| AIX | ppc64be >=power7 | >= 7.2 TL02 | Tier 2 | |
+| AIX | ppc64be >=power7 | >= 7.2 TL04 | Tier 2 | |
 | FreeBSD | x64 | >= 11 | Experimental | Downgraded as of Node.js 12 <sup>[7](#fn7)</sup> |
 
 <em id="fn1">1</em>: GCC 6 is not provided on the base platform. Users will
@@ -171,7 +171,7 @@ Binaries at <https://nodejs.org/download/release/> are produced on:
 
 | Binary package | Platform and Toolchain |
 | --------------------- | ------------------------------------------------------------------------------------------------------------- |
-| aix-ppc64 | AIX 7.1 TL05 on PPC64BE with GCC 6 |
+| aix-ppc64 | AIX 7.2 TL04 on PPC64BE with GCC 8 |
 | darwin-x64 (and .pkg) | macOS 10.15, Xcode Command Line Tools 11 with -mmacosx-version-min=10.13 |
 | linux-arm64 | CentOS 7 with devtoolset-8 / GCC 8 <sup>[8](#fn8)</sup> |
 | linux-armv7l | Cross-compiled on Ubuntu 18.04 x64 with [custom GCC toolchain](https://github.com/rvagg/rpi-newer-crosstools) |