Intel: Drop hard-coded default /fpp Fortran flag on Windows

This flag was added on Windows by the following commits, unfortunately without recording clear reasons:

• commit b761da39, 2008-01-09
• commit e1b2fb4c, 2008-04-30

It is not used by default on other platforms. Since !4659 (merged), we have first-class settings to control use of the preprocessor.

Fixes: #24048
Backport: release