[docs] use = in --max-retries-per-test=N

This is a fixup for #141851

Author: kwk

llvm/docs/CommandGuide/lit.rst

@@ -218,7 +218,7 @@ EXECUTION OPTIONS
 
  Stop execution after the given number of failures.
 
-.. option:: --max-retries-per-test N
+.. option:: --max-retries-per-test=N
 
  Retry running failed tests at most ``N`` times.
  Out of the following options to rerun failed tests the