mpfr 3.1.3: Fix makeinfo error for Linuxbrew
mpfr 3.1.3: Fix makeinfo error for Linuxbrew

Fix error makeinfo: command not found
The mpfr.info timestamp is older than the mpfr.texi timestamp.

maxim-belkin/homebrew-core,maxim-belkin/homebrew-core,forevergenin/homebrew-core,forevergenin/homebrew-core,LinuxbrewTestBot/homebrew-core,Linuxbrew/homebrew-core,LinuxbrewTestBot/homebrew-core,rwhogg/homebrew-core,Linuxbrew/homebrew-core,rwhogg/homebrew-core