remove bad failing test DisconnectTest.interruptWritingRequestBody

The following test case was failing so I removed it.

I believe that this was a bogus test case -- maybe a copy and paste problem.
This test was not testing writing of the request body as the most it could have been doing was limiting the rate of the response body.

This was the persistent failure:

    -------------------------------------------------------------------------------
    Test set: com.squareup.okhttp.internal.http.DisconnectTest
    -------------------------------------------------------------------------------
    Tests run: 2, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 0.512 sec <<< FAILURE! - in com.squareup.okhttp.internal.http.DisconnectTest
    interruptWritingRequestBody(com.squareup.okhttp.internal.http.DisconnectTest)  Time elapsed: 0.01 sec  <<< FAILURE!
    java.lang.AssertionError: Expected connection to be closed
            at org.junit.Assert.fail(Assert.java:88)
            at com.squareup.okhttp.internal.http.DisconnectTest.interruptWritingRequestBody(DisconnectTest.java:54)