Clarify zero-size chunk comment in HTTP response parsing.

The previous "still zero" wording leaned on the reader tracking that contentRemaining was zero on entry and remained zero after parsing the next chunk size. State the actual meaning instead: a zero-size chunk terminates the response.

src/common/io/http/response.c

@@ -145,7 +145,7 @@ httpResponseRead(THIS_VOID, Buffer *const buffer, const bool block)
                         // Read length of next chunk
                         this->contentRemaining = cvtZToUInt64Base(strZ(strTrim(ioReadLine(rawRead))), 16);
 
-                        // If content remaining is still zero then eof
+                        // A zero-size chunk terminates the response
                         if (this->contentRemaining == 0)
                             this->contentEof = true;
                     }