treewide: cleanup error string formatting

Change-Id: I9012ba58dded916984468219b214200144a439b9
Reviewed-on: https://review.monogon.dev/c/monogon/+/3023
Reviewed-by: Serge Bazanski <serge@monogon.tech>
Vouch-Run-CI: Tim Windelschmidt <tim@monogon.tech>
Tested-by: Jenkins CI
diff --git a/metropolis/pkg/fat32/fat32.go b/metropolis/pkg/fat32/fat32.go
index 5d26694..7a45aa4 100644
--- a/metropolis/pkg/fat32/fat32.go
+++ b/metropolis/pkg/fat32/fat32.go
@@ -431,7 +431,7 @@
 
 	allocClusters := len(p.fat)
 	if allocClusters >= fatMask&math.MaxUint32 {
-		return fmt.Errorf("filesystem contains more than 2^28 FAT entries, this is unsupported. Note that this package currently always creates minimal clusters.")
+		return fmt.Errorf("filesystem contains more than 2^28 FAT entries, this is unsupported. Note that this package currently always creates minimal clusters")
 	}
 
 	// Fill out FAT to minimum size for FAT32
diff --git a/metropolis/pkg/verity/encoder.go b/metropolis/pkg/verity/encoder.go
index 871cec0..b28e01d 100644
--- a/metropolis/pkg/verity/encoder.go
+++ b/metropolis/pkg/verity/encoder.go
@@ -532,9 +532,9 @@
 func (e *encoder) MappingTable(dataDevicePath, hashDevicePath string, hashStart int64) (*MappingTable, error) {
 	if e.rootHash == nil {
 		if e.bottom.Len() != 0 {
-			return nil, fmt.Errorf("encoder wasn't closed.")
+			return nil, fmt.Errorf("encoder wasn't closed")
 		}
-		return nil, fmt.Errorf("encoder is empty.")
+		return nil, fmt.Errorf("encoder is empty")
 	}
 
 	if e.writeSb {