Prometheus: Revert stepMode functionality (#38982)

* Revert "Prometheus: add functionality to specify desired step interval in dashboards panels (#36422)"

This reverts commit ddf5b65c51.
Co-authored-by: Ivana Huckova <ivana.huckova@gmail.com>

* Revert "Explore: add functionality for supporting different step modes in prometheus (#37829)"

This reverts commit f433cfd8d9.
Co-authored-by: Ivana Huckova <ivana.huckova@gmail.com>

* Revert stepMode BE implementation from #36796
Co-authored-by: "Ivana Huckova" <ivana.huckova@gmail.com>

public/app/plugins/datasource/prometheus/components/__snapshots__/PromExploreQueryEditor.test.tsx.snap

@@ -16,8 +16,7 @@ exports[`PromExploreQueryEditor should render component 1`] = `
       onChange={[MockFunction]}
       onKeyDownFunc={[Function]}
       onQueryTypeChange={[Function]}
-      onStepIntervalChange={[Function]}
-      onStepModeChange={[Function]}
+      onStepChange={[Function]}
       query={
         Object {
           "expr": "",
@@ -26,7 +25,6 @@ exports[`PromExploreQueryEditor should render component 1`] = `
         }
       }
       queryType="both"
-      stepMode="min"
       stepValue="1s"
     />
   }

public/app/plugins/datasource/prometheus/components/__snapshots__/PromQueryEditor.test.tsx.snap

@@ -31,7 +31,8 @@ exports[`Render PromQueryEditor with basic options should render 1`] = `
         <FormLabel
           tooltip={
             <React.Fragment>
-              Use 'Minimum' or 'Maximum' step mode to set the lower or upper bounds respectively on the interval between data points. For example, set "minimum 1h" to hint that measurements were not taken more frequently. Use the 'Exact' step mode to set an exact interval between data points. 
+              An additional lower limit for the step parameter of the Prometheus query and for the
+               
               <code>
                 $__interval
               </code>
@@ -39,47 +40,18 @@ exports[`Render PromQueryEditor with basic options should render 1`] = `
               <code>
                 $__rate_interval
               </code>
-               are supported.
+               variables. The limit is absolute and not modified by the "Resolution" setting.
             </React.Fragment>
           }
-          width={5}
+          width={7}
         >
-          Step
+          Min step
         </FormLabel>
-        <Select
-          className="select-container"
-          isSearchable={false}
-          menuShouldPortal={true}
-          onChange={[Function]}
-          options={
-            Array [
-              Object {
-                "label": "Minimum",
-                "value": "min",
-              },
-              Object {
-                "label": "Maximum",
-                "value": "max",
-              },
-              Object {
-                "label": "Exact",
-                "value": "exact",
-              },
-            ]
-          }
-          value={
-            Object {
-              "label": "Minimum",
-              "value": "min",
-            }
-          }
-          width={16}
-        />
         <input
-          className="gf-form-input width-4"
+          className="gf-form-input width-8"
           onBlur={[Function]}
           onChange={[Function]}
-          placeholder="15s"
+          placeholder=""
           type="text"
           value=""
         />
@@ -192,7 +164,6 @@ exports[`Render PromQueryEditor with basic options should render 1`] = `
                 "interval": "",
                 "legendFormat": "",
                 "refId": "A",
-                "stepMode": "min",
               }
             }
           />