proto_{alpha,011}: reduce script_typed_ir_size flakiness

Context

The test test_script_typed_ir_size induces flakiness. The goal of this MR is to relax constants until we're happy.

Manually testing the MR

Launch the test many times and observe that it does go through. In lib_protocol/test:

for I in `seq 30`; do dune exec ./main.exe -- test "script typed ir size" 5 --bail; done

(This only tests value_size which was the flaky one, remove the 5 to test the rest as well)

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, the Development Version section of CHANGES.md for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR