Euler and Quaternion: remove update flag from public API

[WestLangley]

Follow-up to #16755.

Migration docs updated separately.

[WestLangley]

Note: the TS files are not consistent in setting return values. For example:

set( x: number, y: number, z: number, w: number ): Quaternion;
clone(): this;
copy( q: Quaternion ): this;
setFromEuler( euler: Euler ): Quaternion;

/ping @Mugen87 @looeee

[mrdoob]

Thanks!