README.md: remove items duplicated from RELNOTES

Added on commit 6d740d7 ("RELNOTES and README.md - existing
functionality modified for the next version", 2022-08-29).

The duplication makes it harder to maintain the RELNOTES, especially
because the contents are prone to diverge between each file.

For example, even though the commit in question (6d740d7) added the
same items to both files, the additions to RELNOTES had two typos, while
the additions to README.md had one typo.

The typos in RELNOTES were fixed by commit c5e8d5d ("typo fixes for
RELNOTES", 2022-08-29), and the typo in README.md was fixed by commit
2ac8a93 ("typo fix for README.md", 2022-08-29), both from PR #5349.

README.md

@@ -184,15 +184,6 @@ We also keep a list of profile fixes for previous released versions in [etc-fixe
 
 Milestone page: https://github.com/netblue30/firejail/milestone/1
 
-### Modified functionality
-
-  * modif:  removed cgroups commands (#5190)
-  * modif: changed --disable-firetunnel into --enable-firetunnel in configure.ac (#5190)
-  * modif: disabled chroot by default in /etc/firejail/firejail.config (#5190)
-  * modif: shell none set as default (#5190)
-  * modif: removed --shell= (#5190)
-  * modif: private-lib disabled by default in /etc/firejail/firejail.config (#5190)
-
 ### Restrict namespaces
 
 `````