codespell: Fix word spelling issues

See,
```
$ codespell --skip=".git,./vendor" --ignore-words-list=calle
./exporter.go:262: overriden ==> overridden
./collector/dfsr.go:132: receieved ==> received
./collector/dns.go:140: reponses ==> responses
./collector/exchange.go:238: occational ==> occasional
./collector/mssql.go:1961: shoud ==> should
./collector/process.go:137: sharable ==> shareable
./collector/remote_fx.go:64: seccond ==> second
./docs/collector.dfsr.md:47: fils ==> fills, files, file
./docs/collector.exchange.md:39: lengt ==> length
./docs/collector.fsrmquota.md:3: Ressource ==> Resource
./docs/collector.fsrmquota.md:51: Ressource ==> Resource
./docs/collector.os.md:20: sotred ==> sorted, stored
./docs/collector.process.md:56: sharable ==> shareable
./docs/collector.smtp.md:27: mailformed ==> malformed
```

Signed-off-by: Mario Trangoni <mjtrangoni@gmail.com>

collector/dfsr.go

@@ -129,7 +129,7 @@ func NewDFSRCollector() (Collector, error) {
 
 		ConnectionFilesReceivedTotal: prometheus.NewDesc(
 			prometheus.BuildFQName(Namespace, subsystem, "connection_received_files_total"),
-			"Total number of files receieved for connection",
+			"Total number of files received for connection",
 			[]string{"name"},
 			nil,
 		),

collector/dns.go

@@ -137,7 +137,7 @@ func NewDNSCollector() (Collector, error) {
 		),
 		Responses: prometheus.NewDesc(
 			prometheus.BuildFQName(Namespace, subsystem, "responses_total"),
-			"Number of reponses sent by DNS server",
+			"Number of responses sent by DNS server",
 			[]string{"protocol"},
 			nil,
 		),

collector/exchange.go

@@ -235,7 +235,7 @@ func (c *exchangeCollector) collectADAccessProcesses(ctx *ScrapeContext, ch chan
 		}
 
 		// since we're not including the PID suffix from the instance names in the label names,
-		// we get an occational duplicate. This seems to affect about 4 instances only on this object.
+		// we get an occasional duplicate. This seems to affect about 4 instances only on this object.
 		labelUseCount[labelName]++
 		if labelUseCount[labelName] > 1 {
 			labelName = fmt.Sprintf("%s_%d", labelName, labelUseCount[labelName])

collector/mssql.go

@@ -1958,7 +1958,7 @@ func (c *MSSQLCollector) Collect(ctx *ScrapeContext, ch chan<- prometheus.Metric
 	}
 	wg.Wait()
 
-	// this shoud return an error if any? some? children errord.
+	// this should return an error if any? some? children errord.
 	if c.mssqlChildCollectorFailure > 0 {
 		return errors.New("at least one child collector failed")
 	}

collector/process.go

@@ -134,7 +134,7 @@ func newProcessCollector() (Collector, error) {
 		),
 		WorkingSetPrivate: prometheus.NewDesc(
 			prometheus.BuildFQName(Namespace, subsystem, "working_set_private_bytes"),
-			"Size of the working set, in bytes, that is use for this process only and not shared nor sharable by other processes.",
+			"Size of the working set, in bytes, that is use for this process only and not shared nor shareable by other processes.",
 			[]string{"process", "process_id", "creating_process_id"},
 			nil,
 		),

collector/remote_fx.go

@@ -61,7 +61,7 @@ func NewRemoteFx() (Collector, error) {
 		),
 		CurrentTCPBandwidth: prometheus.NewDesc(
 			prometheus.BuildFQName(Namespace, subsystem, "net_current_tcp_bandwidth"),
-			"TCP Bandwidth detected in bytes per seccond.",
+			"TCP Bandwidth detected in bytes per second.",
 			[]string{"session_name"},
 			nil,
 		),