Pin httpx till upstream gets resolved

[sl0thentr0py]

starlette CI is broken with

 module 'httpx._types' has no attribute 'URLTypes' 

caused by this change
github.com/encode/httpx/pull/3245

upstream discussion: encode/httpx#3287

[codecov]

❌ 4 Tests Failed:

Tests completed	Failed	Passed	Skipped
11370	4	11366	1635

View the top 3 failed tests by shortest run time

tests.integrations.aws_lambda.test_aws test_init_error[python3.12] 

Stack Traces | 12.4s run time

.../integrations/aws_lambda/test_aws.py:334: in test_init_error (event,) = envelope_items E ValueError: not enough values to unpack (expected 1, got 0) 

tests.integrations.aws_lambda.test_aws test_init_error[python3.11] 

Stack Traces | 17.1s run time

.../integrations/aws_lambda/test_aws.py:334: in test_init_error (event,) = envelope_items E ValueError: not enough values to unpack (expected 1, got 0) 

tests.integrations.aws_lambda.test_aws test_init_error[python3.10] 

Stack Traces | 17.3s run time

.../integrations/aws_lambda/test_aws.py:334: in test_init_error (event,) = envelope_items E ValueError: not enough values to unpack (expected 1, got 0) 

To view individual test run time comparison to the main branch, go to the Test Analytics Dashboard