centos-7-i386: SIGFPE while building dochtml

[mkoeppe]

Reported for Sage 9.4.rc1 at
https://groups.google.com/g/sage-release/c/ocdEAV4pFMo/m/4BEdJZQ8BAAJ
and several times previously.

CC: @sagetrac-tmonteil

Component: porting

Issue created by migration from https://trac.sagemath.org/ticket/32768

[fchapoton]

comment:1

bump to 9.6

[orlitzky]

We no longer support this platform. Giving up.