test: fix visibility issues in Cypress test

Author: haoqunjiang

packages/@vue/cli-ui/tests/e2e/specs/g2-plugins.js

@@ -9,12 +9,14 @@ describe('Plugins', () => {
     cy.get('[data-testid="add-plugin"]').click()
     cy.get('.project-plugins-add').should('be.visible')
     // Search
+    cy.get('.instant-search-input input').clear().type('pwa')
     cy.get('.package-search-item:contains("@vue/cli-plugin-pwa")').should('be.visible')
     cy.get('.instant-search-input input').clear().type('unit-jest')
     cy.get('.package-search-item:contains("@vue/cli-plugin-pwa")').should('be.not.visible')
     cy.get('.package-search-item:contains("@vue/cli-plugin-unit-jest")').should('be.visible')
     cy.get('.instant-search-input input').clear()
     // Install
+    cy.get('.instant-search-input input').clear().type('pwa')
     cy.get('.package-search-item:contains("@vue/cli-plugin-pwa") [data-testid="name"]').should('be.visible').click()
     cy.get('[data-testid="download-plugin"]:contains("@vue/cli-plugin-pwa")').should('not.have.class', 'disabled').click()
     cy.get('.loading-screen .vue-ui-loading-indicator').should('be.visible')