LibC: Fix dumb off-by-two in fgets() :^)

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Libraries/LibC/stdio.cpp

@@ -108,7 +108,7 @@ char* fgets(char* buffer, int size, FILE* stream)
     ASSERT(stream);
     ASSERT(size);
     ssize_t nread = 0;
-    while (nread < (size + 1)) {
+    while (nread < (size - 1)) {
         int ch = fgetc(stream);
         if (ch == EOF)
             break;