Removing Field Target for @Gauge, it is not supported by metrics-cdi :(

Signed-off-by: Raymond Lam <lamr@ca.ibm.com>

api/src/main/java/org/eclipse/microprofile/metrics/annotation/Gauge.java

@@ -58,7 +58,7 @@
  */
 @InterceptorBinding
 @Retention(RetentionPolicy.RUNTIME)
-@Target({ ElementType.METHOD, ElementType.FIELD, ElementType.ANNOTATION_TYPE })
+@Target({ ElementType.METHOD, ElementType.ANNOTATION_TYPE })
 public @interface Gauge {
 
     /**

spec/src/main/asciidoc/metrics_spec.adoc

@@ -1079,7 +1079,7 @@ The following Annotations exist, see below for common fields:
 |Annotation | Applies to |  Description | Default Unit
 
 |@Counted | M, C, T | Denotes a counter, which counts the invocations of the annotated object. | MetricUnits.NONE
-|@Gauge   | M, F | Denotes a gauge, which samples the value of the annotated object.  | _none_ Must be supplied by the user
+|@Gauge   | M | Denotes a gauge, which samples the value of the annotated object.  | _none_ Must be supplied by the user
 |@Metered | M, C, T  | Denotes a meter, which tracks the frequency of invocations of the annotated object. | MetricUnits.PER_SECOND
 |@Metric  | M, F, P | An annotation requesting that a metric should be injected. This annotation can be used on the fields
     of type `Meter`, `Timer`, `Counter`, and `Histogram`. | MetricUnits.NONE
@@ -1207,27 +1207,15 @@ public class CounterBean {
 ----
 
 ==== @Gauge
-An annotation for marking a method or field as a gauge.
+An annotation for marking a method as a gauge.
 
-The implementation must support the following annotation targets:
+The implementation must support the following annotation target:
 
-  * `FIELD`
   * `METHOD`
 
 
 The following lists the behavior for each annotation target.
 
-===== FIELD
-
-When a field is annotated, the implementation must register a gauge for the field using the <<annotated-naming-convention>>. The gauge value and type is equal to the annotated field value and type.
-
-.Example of an annotated field
-[source, java]
-----
-@Gauge
-long value;
-----
-
 ===== METHOD
 
 When a method is annotated, the implementation must register a gauge for the method using the <<annotated-naming-convention>>. The gauge value and type is equal to the annotated method return value and type.
@@ -1346,7 +1334,7 @@ public class TimedBean {
 
 ==== @Metric
 
-An annotation requesting that a metric should be injected or registered. This annotation can be used on the fields of type `Meter`, `Timer`, `Counter`, and `Histogram`.
+An annotation requesting that a metric should be injected or registered.
 
 The implementation must support the following annotation targets:
 
@@ -1375,6 +1363,7 @@ Gauge<Double> hitPercentage = new Gauge<Double>() {
 ----
 
 When a metric injected field is annotated, the implementation must provide the registered metric with the given name (using the <<annotated-naming-convention>>) if the metric already exist. If no metric exists with the given name then the implementation must produce and register the requested metric.
+`@Metric` can only be used on injected fields of type `Meter`, `Timer`, `Counter`, and `Histogram`.
 
 .Example of an injected field
 [source, java]