[llvm] [GlobalISel][NFC]Update the comments of XXLegalizerInfo (PR #76918)

[Matt Arsenault via llvm-commits]

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@@ -23,7 +23,8 @@ namespace llvm {
 
 class ARMSubtarget;
 
-/// This class provides the information for the target register banks.
+/// This class provides the information for the ARM target legalizer for
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arsenm wrote:

I'd just delete the comment from all the target implementations altogether 

https://github.com/llvm/llvm-project/pull/76918