Fix typo and rename Redis to Valkey in the utils/lru/README (#314)

This utils/lru/README incorrectly refers to REDIS_LRU_CLOCK_RESOLUTION
in server.h to modify the LRU clock resolution. However, the actual
constant in server.h has been updated to LRU_CLOCK_RESOLUTION, but the
README was not updated to reflect this change.

1. Replaced REDIS_LRU_CLOCK_RESOLUTION with LRU_CLOCK_RESOLUTION in the
text of utils/lru/README.
2. Updated references from "Redis" to "Valkey" within the same README
file as part of the ongoing rebranding efforts:)

---------

Signed-off-by: Sher Sun <[email protected]>
Co-authored-by: Sher Sun <[email protected]>

utils/lru/README

@@ -1,9 +1,9 @@
 The test-lru.rb program can be used in order to check the behavior of the
-Redis approximated LRU algorithm against the theoretical output of true
+Valkey approximated LRU algorithm against the theoretical output of true
 LRU algorithm.
 
-In order to use the program you need to recompile Redis setting the define
-REDIS_LRU_CLOCK_RESOLUTION to 1, by editing the file server.h.
+In order to use the program you need to recompile Valkey setting the define
+LRU_CLOCK_RESOLUTION to 1, by editing the file server.h.
 This allows to execute the program in a fast way since the 1 ms resolution
 is enough for all the objects to have a different enough time stamp during
 the test.