Bump lineLength to 120 in .swift-format

This seems to be a reasonable limit still readable on most devices, while reducing the amount of reformatting applied by `swift format` checks.

Author: MaxDesiatov

.swift-format

@@ -11,7 +11,7 @@
   "lineBreakBeforeControlFlowKeywords" : false,
   "lineBreakBeforeEachArgument" : true,
   "lineBreakBeforeEachGenericRequirement" : false,
-  "lineLength" : 100,
+  "lineLength" : 120,
   "maximumBlankLines" : 1,
   "multiElementCollectionTrailingCommas" : true,
   "noAssignmentInExpressions" : {