K2 CLI: minor, remove misleading warning

Light tree is used by default now, so it's no longer far from being
production-ready.

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/CommonCompilerArguments.kt

@@ -534,7 +534,7 @@ abstract class CommonCompilerArguments : CommonToolArguments() {
 
     @Argument(
         value = "-Xuse-fir-lt",
-        description = "Compile using LightTree parser with Front-end IR. Warning: this feature is far from being production-ready"
+        description = "Compile using LightTree parser with Front-end IR"
     )
     var useFirLT = true
         set(value) {

compiler/testData/cli/js/jsExtraHelp.out

@@ -133,7 +133,7 @@ where advanced options include:
                              Eliminate builder inference restrictions like allowance of returning type variables of a builder inference call
   -Xuse-fir-extended-checkers Use extended analysis mode based on Front-end IR. Warning: this feature is far from being production-ready
   -Xuse-fir-ic               Compile using Front-end IR internal incremental compilation cycle. Warning: this feature is far from being production-ready
-  -Xuse-fir-lt               Compile using LightTree parser with Front-end IR. Warning: this feature is far from being production-ready
+  -Xuse-fir-lt               Compile using LightTree parser with Front-end IR
   -Xuse-k2                   Compile using experimental K2. K2 is a new compiler pipeline, no compatibility guarantees are yet provided
   -Xuse-mixed-named-arguments Enable Support named arguments in their own position even if the result appears as mixed
   -Xverbose-phases           Be verbose while performing these backend phases

compiler/testData/cli/jvm/extraHelp.out

@@ -226,7 +226,7 @@ where advanced options include:
                              Eliminate builder inference restrictions like allowance of returning type variables of a builder inference call
   -Xuse-fir-extended-checkers Use extended analysis mode based on Front-end IR. Warning: this feature is far from being production-ready
   -Xuse-fir-ic               Compile using Front-end IR internal incremental compilation cycle. Warning: this feature is far from being production-ready
-  -Xuse-fir-lt               Compile using LightTree parser with Front-end IR. Warning: this feature is far from being production-ready
+  -Xuse-fir-lt               Compile using LightTree parser with Front-end IR
   -Xuse-k2                   Compile using experimental K2. K2 is a new compiler pipeline, no compatibility guarantees are yet provided
   -Xuse-mixed-named-arguments Enable Support named arguments in their own position even if the result appears as mixed
   -Xverbose-phases           Be verbose while performing these backend phases