Add libmpfr-dev to apt deps (required by gdb)

Bypass-Presubmit-Reason: no presubmits
Change-Id: Idfb6a459b67ebdffc44ff6e29dbb9eb85696ba07

install-prereqs.sh

diff --git a/install-prereqs.sh b/install-prereqs.sh
index 058a47d..66785b7 100755
--- a/install-prereqs.sh
+++ b/install-prereqs.sh
@@ -56,6 +56,7 @@
     libglib2.0-dev
     libglib2.0-dev-bin
     libgtk2.0-0
+    libmpfr-dev
     libpixman-1-dev
     libpython3-dev
     libpython3.11