protover: Fix old tor hardcoded version check

When computing old Tor protocol line version in protover, we were looking at
0.2.7.5 twice instead of the specific case for 0.2.9.1-alpha.

Fixes #20810

Signed-off-by: David Goulet <dgoulet@torproject.org>

changes/bug20810

@@ -0,0 +1,4 @@
+  o Minor bugfixes (relay)
+    - When computing old Tor protocol line version in protover, we were
+      looking at 0.2.7.5 twice instead of a specific case for 0.2.9.1-alpha.
+      Bugfix on tor-0.2.9.4-alpha.

src/or/protover.c

@@ -697,7 +697,7 @@ protover_compute_for_old_tor(const char *version)
   if (tor_version_as_new_as(version,
                             FIRST_TOR_VERSION_TO_ADVERTISE_PROTOCOLS)) {
     return "";
-  } else if (tor_version_as_new_as(version, "0.2.7.5")) {
+  } else if (tor_version_as_new_as(version, "0.2.9.1-alpha")) {
     /* 0.2.9.1-alpha HSRend=2 */
     return "Cons=1-2 Desc=1-2 DirCache=1 HSDir=1 HSIntro=3 HSRend=1-2 "
       "Link=1-4 LinkAuth=1 "