docs: fix a typo in hacking.html.in

Signed-off-by: NWang Rui <moon.wangrui@huawei.com>
Signed-off-by: NEric Blake <eblake@redhat.com>

HACKING

@@ -109,7 +109,7 @@ issues, such as leaks or use of uninitialized variables.
 
 Some tests are skipped by default in a development environment, based on the
 time they take in comparison to the likelihood that those tests will turn up
-problems during incremental builds. These tests default to being run when when
+problems during incremental builds. These tests default to being run when
 building from a tarball or with the configure option --enable-expensive-tests;
 you can also force a one-time toggle of these tests by setting
 VIR_TEST_EXPENSIVE to 0 or 1 at make time, as in:

docs/hacking.html.in

@@ -122,7 +122,7 @@
           Some tests are skipped by default in a development environment,
           based on the time they take in comparison to the likelihood
           that those tests will turn up problems during incremental builds.
-          These tests default to being run when when building from a
+          These tests default to being run when building from a
           tarball or with the configure option --enable-expensive-tests;
           you can also force a one-time toggle of these tests by
           setting VIR_TEST_EXPENSIVE to 0 or 1 at make time, as in: