Fix sonar bug Font declarations should contain at least one generic font family => DONE

src/app/detail/components/spectra-graph/spectra-graph.component.css

 .titles text {
     fill: #5a5a5a;
-    font-family: "sans-serif";
-    font-weight: "300";
-    font-size: 22px;
+    font-size: 24px;
 }
 
 .axis line {
@@ -11,11 +9,6 @@
     shape-rendering: crispEdges;
 }
 
-.axis text {
-    font-family: sans-serif;
-    font-size: 11px;
-}
-
 .grid line {
     fill: none;
     stroke: lightgray;
@@ -27,11 +20,6 @@
     stroke-width: 1.5px;
 }
 
-.ray text {
-    font-family: "sans-serif";
-    font-size: 15px;
-}
-
 .emission line {
     stroke: steelblue;
 }
@@ -117,8 +105,7 @@
 }
 
 .emission-button text, .absorption-button text {
-    font-size: 13px;
-    font-family: "sans-serif";
+    font-size: 15px;
     color: #333333;
     fill: #333333;
 }
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