Make sure to always truncate the file when writing (#200)

The append action fully rewrites the file, so we should open in truncate
mode in this case as well.

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Fixes #197.

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app/src/main/java/be/chvp/nanoledger/data/LedgerRepository.kt

@@ -142,7 +142,7 @@ class LedgerRepository
                 if (!matches(fileUri)) {
                     onMismatch()
                 } else {
-                    context.contentResolver.openOutputStream(fileUri, "w")
+                    context.contentResolver.openOutputStream(fileUri, "wt")
                         ?.let { OutputStreamWriter(it) }
                         ?.use {
                             fileContents.value!!.forEach { line ->