Match variable name in StringLitOp builders

Update `in_type` to `inType` to match clang-tidy style in the .cpp file. 

Sync after: https://reviews.llvm.org/D110686

Author: clementval

flang/include/flang/Optimizer/Dialect/FIROps.td

@@ -2367,16 +2367,16 @@ def fir_StringLitOp : fir_Op<"string_lit", [NoSideEffect]> {
   let printer = "::print(p, *this);";
 
   let builders = [
-    OpBuilder<(ins "fir::CharacterType":$in_type,
+    OpBuilder<(ins "fir::CharacterType":$inType,
       "llvm::StringRef":$value,
       CArg<"llvm::Optional<int64_t>", "{}">:$len)>,
-    OpBuilder<(ins "fir::CharacterType":$in_type,
+    OpBuilder<(ins "fir::CharacterType":$inType,
       "llvm::ArrayRef<char>":$xlist,
       CArg<"llvm::Optional<int64_t>", "{}">:$len)>,
-    OpBuilder<(ins "fir::CharacterType":$in_type,
+    OpBuilder<(ins "fir::CharacterType":$inType,
       "llvm::ArrayRef<char16_t>":$xlist,
       CArg<"llvm::Optional<int64_t>", "{}">:$len)>,
-    OpBuilder<(ins "fir::CharacterType":$in_type,
+    OpBuilder<(ins "fir::CharacterType":$inType,
       "llvm::ArrayRef<char32_t>":$xlist,
       CArg<"llvm::Optional<int64_t>", "{}">:$len)>];