Fix CodeQL warnings in UnsynchronizedBufferedInputStream: Implicit

narrowing conversion in compound assignment.

- (int count - int pos) here is always an int so amount is also in the
int range if the above test is true.
- We can safely cast and avoid static analysis warnings: "Implicit
narrowing conversion in compound assignment"
- https://github.com/apache/commons-io/security/code-scanning/135
- https://github.com/apache/commons-io/security/code-scanning/88

Author: garydgregory

src/changes/changes.xml

@@ -94,6 +94,9 @@ The <action> type attribute can be add,update,fix,remove.
       <action dev="ggregory" type="fix" due-to="sebbASF">
         [Javadoc] IOUtils#contentEquals does not throw NullPointerException #496.
       </action>
+      <action dev="ggregory" type="fix" due-to="Gary Gregory">
+        Fix CodeQL warnings in UnsynchronizedBufferedInputStream: Implicit narrowing conversion in compound assignment.
+      </action>
       <!-- ADD -->
       <action dev="ggregory" type="add" due-to="Gary Gregory">
         Add org.apache.commons.io.channels.FileChannels.