MutableSequence coverage in ImmutableSandboxedEnvironment

[dylanscott]

I happened to notice in using ImmutableSandboxedEnvironment that the default modifies_known_mutable check seems to be missing coverage for a couple of methods. In particular the clear and pop methods are checked for both MutableMapping and MutableSet but not MutableSequence.

Example:

from jinja2.sandbox import ImmutableSandboxedEnvironment

env = ImmutableSandboxedEnvironment()
print(env.from_string("{{ [1].pop() }}").render())

Expected: SecurityError should be raised
Actual: 1 is printed

Environment:

• Python version: 3.10
• Jinja version: 3.1.4

[dylanscott]

I prepared a PR to add checks for these attributes if the change makes sense #2033