README: Add note about DB fix for Apple Silicon

[sampart]

Description

My colleague @mgriffin encountered this problem, and solved it with the change mentioned. Here's fuller error output from him:

[IMPORTANT]
Don't forget to include the Crash Report log file under
DiagnosticReports directory in bug reports.


FATAL: prematurely zombied
[39268] - Worker 0 (PID: 39439) booted in 0.05s, phase: 0
/Users/mike/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/pg-1.5.6/lib/pg/connection.rb:695: [BUG] Segmentation fault at 0x0000000103ba8abc
ruby 3.2.2 (2023-03-30 revision e51014f9c0) [arm64-darwin23]

-- Crash Report log information --------------------------------------------
   See Crash Report log file in one of the following locations:
     * ~/Library/Logs/DiagnosticReports
     * /Library/Logs/DiagnosticReports
   for more details.
Don't forget to include the above Crash Report log file in bug reports.

-- Control frame information -----------------------------------------------

I've also very slightly tweaked a couple of other bits of the README to hopefully make it clearer.

Type of change

• Documentation update

How Has This Been Tested?

Local setup