[Logs UI] Fix font size references after EUI upstream change (#33411)

This fixes the `small` font scale of the log viewer to correctly reference the EUI font size again. Before this fix, the `small` font scale was rendered larger than `medium`. Similarly, the tick labels of the log minimap were being rendered too large.

Both resulted from a breaking change of the exported variable names in elastic/eui#1590.

fixes #32759

x-pack/plugins/infra/public/components/logging/log_minimap/time_ruler.tsx

@@ -44,7 +44,7 @@ export const TimeRuler: React.SFC<TimeRulerProps> = ({ end, height, start, tickC
 TimeRuler.displayName = 'TimeRuler';
 
 const TimeRulerTickLabel = styled.text`
-  font-size: ${props => props.theme.eui.euiFontSizeXs};
+  font-size: ${props => props.theme.eui.euiFontSizeXS};
   line-height: ${props => props.theme.eui.euiLineHeight};
   fill: ${props => props.theme.eui.textColors.subdued};
 `;

x-pack/plugins/infra/public/components/logging/log_text_stream/item_field.tsx

@@ -15,7 +15,7 @@ export const LogTextStreamItemField = styled.div.attrs<{
     switchProp('scale', {
       large: props.theme.eui.euiFontSizeM,
       medium: props.theme.eui.euiFontSizeS,
-      small: props.theme.eui.euiFontSizeXs,
+      small: props.theme.eui.euiFontSizeXS,
       [switchProp.default]: props.theme.eui.euiFontSize,
     })};
   line-height: ${props => props.theme.eui.euiLineHeight};