[BUGFIX] Raise phpstan processTimeout

Recently from time to time phpstan ci runs are failing with following
error message:

> Reached internal errors count limit of 50, exiting...
> Internal error: Child process timed out after 600.0 seconds.
> Try making it longer with parallel.processTimeout setting.

As a intermediate solution this timeout should be increased.
Deeper investigation and maybe finding a solution to avoid such
long subprocess run times is the more reasonable way - but to
avoid a lot of test failes, better trade a longer runtime in ci
than a linger time to find a proper fix for it as a first solution.

Resolves: #97490
Releases: main, 11.5
Change-Id: I8f5a23f233024090de32ce4b3272d3800fc0c2ab
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74447
Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Elias Häußler <e.haeussler@familie-redlich.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>

Build/phpstan/phpstan.neon

@@ -12,6 +12,9 @@ parameters:
   parallel:
     # Don't be overly greedy on machines with more CPU's to be a good neighbor especially on CI
     maximumNumberOfProcesses: 5
+    # @todo Process timeout raised as a intermediate solution. This should be further investigated if we can mitigate
+    #       the occurring subprocess timeout issue through other configurations and minimize the execution time again.
+    processTimeout: 900.0
 
   level: 5