schemachanger: bump test timeout to avoid timeouts on TenantLogicTest

Previously, we were right at the timeout boundary
for the TenantLogicTest. With the declarative schema
changer enabled we are just past the 45 minute mark causing
this test to fail. This patch bumps up the test timeout to 50
minutes to allow for breathing room.

Release note: None

Makefile

@@ -130,7 +130,7 @@ SUBTESTS :=
 LINTTIMEOUT := 30m
 
 ## Test timeout to use for regular tests.
-TESTTIMEOUT := 45m
+TESTTIMEOUT := 50m
 
 ## Test timeout to use for race tests.
 RACETIMEOUT := 45m